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Count the primes in Collatz sequences

Several Cody problems (21, 69, 42937, 44448, 44784, 52422) involve Collatz sequences. These start with a seed . If is odd, the ...

3 months ago

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List the Moran numbers

The quotient of a Moran number and its digit sum is prime. For example, 117 and 481 are Moran numbers because 117/(1+1+7) is 13 ...

3 months ago

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Easy Sequences 6: Coefficient sums of derivatives

Consider the polynomial function and its first-order derivative . The sums of the coefficients of P and P', are and , respecti...

3 months ago

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Determine whether a number is a fibodiv number

The number 14 is a fibodiv number because you can divide it into 1 and 4, use those numbers as the seeds for a Fibonacci sequenc...

3 months ago

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Determine whether a number is unprimeable

The number 204 is unprimeable because no single digit can be changed to make it prime. In contrast, the number 207 is not unprim...

3 months ago

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Count the ways to draw non-intersecting chords between points on a circle

There are 9 ways to draw non-intersecting chords between four points on the perimeter of a circle (including no chords at all). ...

3 months ago

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Find the nth nude number

The number 672 is a nude number because it openly displays three of its divisors: 6, 7, and 2. In other words, a nude number is ...

3 months ago

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Easy Sequences 9: Faithful Pairs

A "faithful number" is a non-prime number that is one less or one more than some prime number but not both. For example, for num...

3 months ago

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Easy Sequences 10: Sum of Cumsums of Fibonacci Sequence

The function F(n) is defined as the set of Fibonacci numbers from the first up to the n-th. S(n) is the result of applying to F,...

3 months ago

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Easy Sequences 8: Triangles with integer sides and prime perimeters

The triangle below is special. It has integer sides and a prime perimeter. Given an integer "n" we want to know how many t...

3 months ago

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Hoax Numbers

A Hoax Number (OEIS A019506) is defined as a composite number, whose sum of digits is equal to the sum of digits of its distinct...

3 months ago

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Easy Sequences 3: Prime 44-number Squares

The positive integers 62 and 238 are related. Their squares (3844 and 56,644) both end in '44'. In fact, 62 and 238 are the 3rd ...

4 months ago

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Easy Sequences 2: Trigonometric function with integral input and output

The function 'F', defined as: , will always return an integer if the input is a natural number (in radian...

4 months ago

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Double Fibonacci

double_fibonacci takes two integers, each greater than one, as input arguments (it does not have to check the format of the inpu...

4 months ago

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Sort Except Zeros

Sort the numbers in a vector. But the position of zeros should not be changed. Example: sort_except_zeros( [5 3 0 0 2 4] ) == [...

4 months ago

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Which Prime

Given two prime numbers, specify the relation between them i.e. - 'Twin Prime', 'Cousin Prime', 'Sexy Prime' or 'None'

4 months ago

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Bessel Polynomials

Return the n-th Bessel polynomial Assume that n is a non-negative finite integer. bessel_poly(0) ans = 1 bessel_poly(1) ...

5 months ago

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List Honaker primes

The number 131 is the 32nd prime number. It is a Honaker prime because the sum of its digits (1+3+1) equals the sum of the digit...

5 months ago

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Find numbers in the Popular Computing Z-sequence

Here’s a quick one. In 1977 the magazine Popular Computing sought “problem situations for which the computer is the best (if not...

5 months ago

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Gallery function, learning

write a Function, edit something or Add something that give us like the following for random n: n=2 ans= [ 0 1 ...

5 months ago

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Radioisotope Thermoelectric Generator (RTG)

Given an isotope's atomic mass (in amu), half-life (in years(a) or days(d)), and average kinetic energy absorbed (of emitted dec...

5 months ago

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Convert Two Character String into a Binary Vector

Given a string "XOXXO" convert it into a binary vector. [1 0 1 1 0] Paul Berglund implemented an optimal method in <http://ww...

5 months ago

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List the nth prime quartet prefix

Prime numbers larger than 5 can end only in 1, 3, 7, or 9, but of course not all numbers ending in these four digits are prime. ...

5 months ago

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Convert Thermocouple output voltage (in mV) to Temperature (in C)

Convert Thermocouples of types (B,E,J,K,N,R,S,T) output junction voltage (in mV) to temperature (in C) using NIST coefficients r...

5 months ago

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Compute the fractional derivative

Cody Problem 1370 asks us to compute the derivative of a polynomial. This problem extends that idea to fractional derivatives, w...

5 months ago

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Pick the die most likely to win

After discussing Rock, Paper, Scissors, Lizard, Spock in The Simpsons and their Mathematical Secrets, Simon Singh writes that in...

5 months ago

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Compute the sum of reciprocals of quadratics

Write a function to compute the following sum: See also Cody Problem 46000.

5 months ago

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Compute a sum involving the totient over divisors of a number

Write a function to compute the following sum: where is the totient function. The sum is computed over the divisors of (inc...

5 months ago

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Nuclear Binding Energy

Compute the approximate nuclear binding energy in MeV using the least-squares fit of the semi-emirical mass formula. Round to th...

5 months ago

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Compute the effective conductivity of a heterogeneous aquifer

Slow flow through soil or another porous medium follows Darcy’s law, which relates the flow of water to the gradient in piezome...

5 months ago