14 questions linked to/from Find the Factorial!
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### Double Factorial [duplicate]

Challenge The objective is simple, in the shortest amount of bytes, write a function or program that takes a number and prints its double factorial. The input must be taken from stdin or a function ...
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### Tips for golfing in C

What general tips do you have for golfing in C? I'm looking for ideas that can be applied to code golf problems in general that are at least somewhat specific to C (e.g. "remove comments" is not an ...
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### Repeated! Factorials!

Not to be confused with Find the factorial! Introduction The factorial of an integer n can be calculated by $$n!=n\times(n-1)\times(n-2)\times(...)\times2\times1$$...
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### Factorials and never ending cycles!

As you may know it, the factorial of a positive integer n is the product of all the positive integers which are equal or smaller to ...
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### Deranged !Combinatorics: Compute the Subfactorial

The subfactorial or rencontres numbers (A000166) are a sequence of numbers similar to the factorial numbers which show up in the combinatorics of permutations. In particular the nth subfactorial !n ...
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### Last non-zero digit of n!

Given an integer 1 ≤ N ≤ 1,000,000 as input, output the last non-zero digit of N!, where ! is the factorial (the product of all numbers from 1 to N, inclusive). This is OEIS sequence A008904. Your ...
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### Array Escape - get out of there

One day you awake only to find yourself caught in an array. You try to just walk out of there, taking one index at the time, but it seems there are other rules: The array is completely filled with ...
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### Mathematical Combination

Write a program that takes an input such as: n,k which then computes: and then prints the result. A numerical example: Input: ...
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### How much candy can you eat?

Credit to Geobits in TNB for the idea A post without sufficient detail recently posited an interesting game: 2 children sit in front of an array of candy. Each piece of candy is numbered 1 to ...
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### Am I a Pillai prime?

A Pillai prime is a prime number $p$ for which there exists some positive $m$ such that $(m! + 1) \equiv 0 \:(\text{mod } p)$ and $p \not\equiv 1\:(\text{mod }m)$. In other words, an ...
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### Tips for golfing in Swift

What are some tips for code-golfing in Swift? Its focus on safety seems to make it difficult to golf in, but that makes little tips and even more useful. Are there any features in Swift that may help ...
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### Verify Wolstenholme's theorem

Definition Wolstenholme's theorem states that: where a and b are positive integers and p ...