Problem 50913. Compute the nth term from the golden sieve

Created by ChrisR

Solve Later

{"parts":[{"partUri":"/matlab/document.xml","contentType":"application/vnd.mathworks.matlab.code.document+xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\"?><w:document xmlns:w=\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\"><w:body><w:p><w:pPr><w:pStyle w:val=\"text\"/><w:jc w:val=\"left\"/></w:pPr><w:hyperlink w:docLocation=\"https://www.mathworks.com/matlabcentral/cody/problems/45367\"><w:r><w:rPr><w:u/></w:rPr><w:t>Cody Problem 45367</w:t></w:r></w:hyperlink><w:r><w:t> involved the Sieve of Eratosthenes, and </w:t></w:r><w:hyperlink w:docLocation=\"https://www.mathworks.com/matlabcentral/cody/problems/50811-compute-the-nth-term-from-the-sieve-of-flavius-josephus\"><w:r><w:rPr><w:u/></w:rPr><w:t>Cody Problem 50811</w:t></w:r></w:hyperlink><w:r><w:t> involved the Sieve of Flavius Josephus. To apply the </w:t></w:r><w:r><w:rPr><w:i/></w:rPr><w:t>golden sieve</w:t></w:r><w:r><w:t>, start with the natural numbers and at the </w:t></w:r><w:customXml w:element=\"equation\"><w:customXmlPr><w:attr w:name=\"displayStyle\" w:val=\"false\"/><w:attr w:name=\"altTextString\" w:val=\"n\"/></w:customXmlPr><w:r><w:t>n</w:t></w:r></w:customXml><w:r><w:t>th step, take the sequence, which we will call </w:t></w:r><w:customXml w:element=\"equation\"><w:customXmlPr><w:attr w:name=\"displayStyle\" w:val=\"false\"/><w:attr w:name=\"altTextString\" w:val=\"a\"/></w:customXmlPr><w:r><w:t>a</w:t></w:r></w:customXml><w:r><w:t>, and delete the term in the </w:t></w:r><w:customXml w:element=\"equation\"><w:customXmlPr><w:attr w:name=\"displayStyle\" w:val=\"false\"/><w:attr w:name=\"altTextString\" w:val=\"a(n)\"/></w:customXmlPr><w:r><w:t>a(n)</w:t></w:r></w:customXml><w:r><w:t> position. </w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/><w:jc w:val=\"left\"/></w:pPr><w:r><w:t>In the first step, delete the term in the </w:t></w:r><w:customXml w:element=\"equation\"><w:customXmlPr><w:attr w:name=\"displayStyle\" w:val=\"false\"/></w:customXmlPr><w:r><w:t>a(1) = 1</w:t></w:r></w:customXml><w:r><w:t> position to get 2, 3, 4, 5, 6, 7,…Then in the second step, delete the term in the </w:t></w:r><w:customXml w:element=\"equation\"><w:customXmlPr><w:attr w:name=\"displayStyle\" w:val=\"false\"/><w:attr w:name=\"altTextString\" w:val=\"a(2) = 3\"/></w:customXmlPr><w:r><w:t>a(2) = 3</w:t></w:r></w:customXml><w:r><w:t> position (i.e., 4) to get 2, 3, 5, 6, 7, 8, 9,…In the third step, delete the term in the </w:t></w:r><w:customXml w:element=\"equation\"><w:customXmlPr><w:attr w:name=\"displayStyle\" w:val=\"false\"/><w:attr w:name=\"altTextString\" w:val=\"a(3) = 5\"/></w:customXmlPr><w:r><w:t>a(3) = 5</w:t></w:r></w:customXml><w:r><w:t> position (i.e., 7) to get 2, 3, 5, 6, 8, 9, 10,…Et cetera.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/><w:jc w:val=\"left\"/></w:pPr><w:r><w:t>Write a function that returns the </w:t></w:r><w:customXml w:element=\"equation\"><w:customXmlPr><w:attr w:name=\"displayStyle\" w:val=\"false\"/><w:attr w:name=\"altTextString\" w:val=\"n\"/></w:customXmlPr><w:r><w:t>n</w:t></w:r></w:customXml><w:r><w:t>th term in the sequence after an infinite number of steps.</w:t></w:r></w:p></w:body></w:document>","relationship":null}],"relationships":[{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/document","target":"/matlab/document.xml","relationshipId":"rId1"}]}

<div style = "text-align: start; line-height: 20.4333px; min-height: 0px; white-space: normal; color: rgb(0, 0, 0); font-family: Menlo, Monaco, Consolas, monospace; font-style: normal; font-size: 14px; font-weight: 400; text-decoration: rgb(0, 0, 0); white-space: normal; "><div style="block-size: 165px; display: block; min-width: 0px; padding-block-start: 0px; padding-top: 0px; perspective-origin: 407px 82.5px; transform-origin: 407px 82.5px; vertical-align: baseline; "><div style="block-size: 63px; font-family: Helvetica, Arial, sans-serif; line-height: 21px; margin-block-end: 9px; margin-block-start: 2px; margin-bottom: 9px; margin-inline-end: 10px; margin-inline-start: 4px; margin-left: 4px; margin-right: 10px; margin-top: 2px; perspective-origin: 384px 31.5px; text-align: left; transform-origin: 384px 31.5px; white-space: pre-wrap; margin-left: 4px; margin-top: 2px; margin-bottom: 9px; margin-right: 10px; "><a target='_blank' href = "https://www.mathworks.com/matlabcentral/cody/problems/45367">Cody Problem 45367</a><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 129.5px 8px; transform-origin: 129.5px 8px; unicode-bidi: normal; "> involved the Sieve of Eratosthenes, and <a target='_blank' href = "https://www.mathworks.com/matlabcentral/cody/problems/50811-compute-the-nth-term-from-the-sieve-of-flavius-josephus">Cody Problem 50811</a><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 94px 8px; transform-origin: 94px 8px; unicode-bidi: normal; "> involved the Sieve of Flavius Josephus. To apply the <span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 39.5px 8px; transform-origin: 39.5px 8px; unicode-bidi: normal; ">golden sieve<span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 133.5px 8px; transform-origin: 133.5px 8px; unicode-bidi: normal; ">, start with the natural numbers and at the n<span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 129px 8px; transform-origin: 129px 8px; unicode-bidi: normal; ">th step, take the sequence, which we will call a<span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 87px 8px; transform-origin: 87px 8px; unicode-bidi: normal; ">, and delete the term in the <img src="data:image/png;base64,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" alt="a(n)" style="width: 29.5px; height: 18.5px;" width="29.5" height="18.5"><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 30.5px 8px; transform-origin: 30.5px 8px; unicode-bidi: normal; "> position. </div><div style="block-size: 63px; font-family: Helvetica, Arial, sans-serif; line-height: 21px; margin-block-end: 9px; margin-block-start: 2px; margin-bottom: 9px; margin-inline-end: 10px; margin-inline-start: 4px; margin-left: 4px; margin-right: 10px; margin-top: 2px; perspective-origin: 384px 31.5px; text-align: left; transform-origin: 384px 31.5px; white-space: pre-wrap; margin-left: 4px; margin-top: 2px; margin-bottom: 9px; margin-right: 10px; "><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 119.5px 8px; transform-origin: 119.5px 8px; unicode-bidi: normal; ">In the first step, delete the term in the <img src="data:image/png;base64,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" style="width: 56px; height: 18.5px;" width="56" height="18.5"><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 231.5px 8px; transform-origin: 231.5px 8px; unicode-bidi: normal; "> position to get 2, 3, 4, 5, 6, 7,…Then in the second step, delete the term in the <img src="data:image/png;base64,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" alt="a(2) = 3" style="width: 56px; height: 18.5px;" width="56" height="18.5"><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 256px 8px; transform-origin: 256px 8px; unicode-bidi: normal; "> position (i.e., 4) to get 2, 3, 5, 6, 7, 8, 9,…In the third step, delete the term in the <img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAHAAAAAlCAYAAACao20PAAADG0lEQVR4nO2a4bGrIBCFvx7swAZswApSQTqwg3RgC9aQEuwhLaSGtHDfD9mRKMiK+NQMZ4aZzEQQWPbs2UXIyMjIyMjI2BsF0CQcrwaqhONlLKAAetJueAE8gXvCMTMcKIAXeuPVphUrxv4FIxaMa5+2G9AeNbEeeASeqRi86W/SeqAM9C2AN9en0wfz9dutPmpS78AzFfAxzz1MezFO/EPYGxvT56ooGNbpM15/5KSW6E2ecYmbO+MCQh4M4wG4IuSga8LGf4PG+x4sK9M3gwGfyvd9dFM7HT4cGON80EwqlFb0DAbULK40z15N0AjTNJwojt8YJnXbOI54oHZhb3TeeibIGu2Y37GTMSvmEr9mrhRbM5ktnF6j9z7Bk2vRqB3nXa0jQVwsGOPL0/zuGY3k8hChvliIMl0rSkSKh1IP3zt9ediathal6dfgT6WijVjhprGCb5ef4kOc9C2Z50Mt+gVI35iNlEO3paXw/pK5IaPUtXiBLwbZbu76b60B76aPnQOuPYVCuzFCpjXv2dJSxl+bXjW58Bds47k2w/ZA1/9bk0+hbduImkK4GPCq+eAUdphaxSriBb7qhqhMn1BJVT2w36MZ79cMKKmR9gAD367rSwM6lg2csvwjh0kTX1KlL2eCrF9tQBEtviqKfSp8Ev9NOgMKlWoMuEXEHKVCQxBxpYrrFWHjdIR5eWsaYUOMoi2nxeafZ1GhU4gHqlKjxpqMi4Zqvifs26gt+dgUcmA0tNgTrr/6cDYVCiPbqW9abOU33TBRppKjyKB35vwsnrw1FslthTaNkDLUVSC07YMcXjU126rPptCaYXPsxL5lMJ7vGuRNeDOFHlwXt3Lbrr2sFXY45OIzAjbbudYoYnK1oraLqy/TxHjwzfdLd1hSflvynGkhtzP9WvPfmipMRzx9HoFpOLLXL6EgisEKxnjg+mioMf81LG+u5kK3ZB57HqbPGiEi77pa+rC0/lPgRkQZKAKyCRk7oGNfYSHx+VSfI/waevahhV/5Iu0S6EhrxD0+Fs4IIKXI0H78m5GRkZGRkZGRcTb8A/oNdpREGA/GAAAAAElFTkSuQmCC" alt="a(3) = 5" style="width: 56px; height: 18.5px;" width="56" height="18.5"><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 52.7167px 8px; transform-origin: 52.7167px 8px; unicode-bidi: normal; "> position (i.e., 7) to get 2, 3, 5, 6, 8, 9, 10,…Et cetera.</div><div style="block-size: 21px; font-family: Helvetica, Arial, sans-serif; line-height: 21px; margin-block-end: 9px; margin-block-start: 2px; margin-bottom: 9px; margin-inline-end: 10px; margin-inline-start: 4px; margin-left: 4px; margin-right: 10px; margin-top: 2px; perspective-origin: 384px 10.5px; text-align: left; transform-origin: 384px 10.5px; white-space: pre-wrap; margin-left: 4px; margin-top: 2px; margin-bottom: 9px; margin-right: 10px; "><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 102px 8px; transform-origin: 102px 8px; unicode-bidi: normal; ">Write a function that returns the n<span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 178.5px 8px; transform-origin: 178.5px 8px; unicode-bidi: normal; ">th term in the sequence after an infinite number of steps.</div></div></div>

Solve

Solution Stats

11 Solutions
11 Solvers

Last Solution submitted on Aug 01, 2022

Last 200 Solutions

Problem Comments

3 Comments

3 Comments

ChrisR on 12 Mar 2021

OK, but you can you *derive* that formula?

Tim on 12 Mar 2021

Does “look up in OEIS” count as “derive”?

ChrisR on 13 Mar 2021

Tim: You, William, David, and others have figured me out. I suppose there are worse habits than repeatedly clicking the "Webcam" button on OEIS.

Problem Recent Solvers11

Problem Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Problem 50913. Compute the nth term from the golden sieve

Solution Stats

Last 200 Solutions

Problem Comments

Problem Recent Solvers11

Suggested Problems

More from this Author166

Problem Tags

Community Treasure Hunt

Problem 50913. Compute the nth term from the golden sieve

Solution Stats

Last 200 Solutions

Problem Comments

Problem Recent Solvers11

Suggested Problems

More from this Author166

Problem Tags

Community Treasure Hunt

Players