# Questions tagged [number]

This challenge is intended to be solved by using, manipulating, accepting as input, or outputting numeric values.

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### Golf a bijection $\mathbb{N}^n\to\mathbb{N}$

Your task is to write a program which implements a bijection $\mathbb{N}^n\to\mathbb{N}$ for $n \ge 1$. Your program should take $n$ natural numbers as input, in any acceptable method (including ...
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### Count the Collatz survivors mod 2^n

Introduction We have 22 Collatz conjecture-related challenges as of October 2020, but none of which cares about the restrictions on counter-examples, if any exists, to the conjecture. Considering a ...
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### We're much closer than you think

Martin Ender's 2D programming language Alice has two different modes depending on what orientation the IP has: orthogonal (Cardinal mode) or diagonal (Ordinal mode). Commands in Alice change their ...
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### Eating Persistence

Intro Find the result of number cannibalism. Why was 6 scared of 7? Becase 7 8 9. Your program will have to find the result of applying the ...
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### Size up a number

Intro Given a whole number $< 100,$ extend/shorten the english representation of the number to have as many characters as it's value. Sandbox Rules Take the number $n$, and get it in words ...
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### Amount Of Potential Keys That'll Fit The Lock

Introduction: You're a key maker, and want to access something from a safe that has a lock. Unfortunately, the key to that lock is lost, so you'll have to make a new one. You have access to a bunch of ...
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### Find a Similar Number

We consider two integers to be similar if, when written in decimal, have the same length, and if we compare characters in any two positions for both decimal strings, the comparison results (less, ...
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### Convert to and from Base 94

The challenge Make 2 programs which convert decimal to and from base 94, or a bidirectional program. Base 94? Base 94 is like any other base, but instead of 0 to 9 and letters, it uses ASCII ...
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### A bit of a digital XOR

Here are the first 100 numbers of a sequence: ...
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### Find the Inverse Neighbor Pairs

Definition We say a pair of integers $(a,b)$, where $0<a<b<N$ and $N$ is an integer larger than 4, is an inverse neighbor pair respect to $N$ if $ab\equiv1\text{ }(\text{mod }N)$ ...
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### Number of palindrome splits

In this task you will take as input a non-negative integer $n$, and output the number of pairs of non-negative integers $a,b$ such that both are palindromes*, $a \leq b$, and $a+b = n$. For ...
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### Power-Ending Patterns

When you look at the last decimal digit of each power of a non-negative integer a repeating pattern forms. For example, 3: ...
The challenge is to implement a program or function (subsequently referred to as "program") that takes a nonnegative integer $n$ as input and returns $n\over\sqrt{2}$ (the input divided by the ...
Given two nonempty arrays of natural numbers $a$ and $b$, return the shortest nonempty array of pairs of natural numbers $q$ such that the sequence of first elements of $q$ consists of a whole ...