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# Tim

Last seen: Today Active since 2012

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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 ...

15 days 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 ...

16 days 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...

22 days 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...

24 days 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...

24 days 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). ...

24 days 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 ...

28 days 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...

29 days 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,...

1 month 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...

1 month 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...

1 month 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 ...

1 month 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...

1 month 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...

2 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] ) == [...

2 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'

2 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) ...

2 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...

2 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...

2 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 ...

3 months ago

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

3 months ago

Solved

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...

3 months ago

Solved

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. ...

3 months ago

Solved

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...

3 months ago

Solved

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...

3 months ago

Solved

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...

3 months ago

Solved

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

3 months ago

Solved

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...

3 months ago

Solved

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...

3 months ago

Solved

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...

3 months ago