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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...

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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). ...

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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 ...

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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...

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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,...

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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...

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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...

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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 ...

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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...

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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...

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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] ) == [...

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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'

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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) ...

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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...

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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...

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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 ...

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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...

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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...

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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. ...

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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...

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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...

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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...

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Compute the sum of reciprocals of quadratics
Write a function to compute the following sum: See also Cody Problem 46000.

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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...

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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...

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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...

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Sum the elements in rows of the Levine triangle
The Levine triangle starts as follows: Row 0: 2 Row 1: 1 1 Row 2: 1 2 Row 3: 1 1 2 To construct each row, r...

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Identify Ruth-Aaron numbers
After Hank Aaron hit his 715th home run and passed Babe Ruth’s total of 714, Carl Pomerance noticed that the union of the prime ...

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Compute a sum of Ramanujan
Srinivasa Ramanujan defined the following function: Write a function to compute for various values of . See also Cody Proble...

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Find the smallest integer m such that n divides m!
Write a function that takes an integer and finds the smallest integer whose factorial is divisible by . For example, if , then...

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