project_euler.problem_014.sol1

Problem 14: https://projecteuler.net/problem=14

Problem Statement: The following iterative sequence is defined for the set of positive integers:

n → n/2 (n is even) n → 3n + 1 (n is odd)

Using the rule above and starting with 13, we generate the following sequence:

13 → 40 → 20 → 10 → 5 → 16 → 8 → 4 → 2 → 1

It can be seen that this sequence (starting at 13 and finishing at 1) contains 10 terms. Although it has not been proved yet (Collatz Problem), it is thought that all starting numbers finish at 1.

Which starting number, under one million, produces the longest chain?

Functions

solution(→ int)

Returns the number under n that generates the longest sequence using the

Module Contents

project_euler.problem_014.sol1.solution(n: int = 1000000) → int

Returns the number under n that generates the longest sequence using the formula: n → n/2 (n is even) n → 3n + 1 (n is odd)

>>> solution(1000000)
837799
>>> solution(200)
171
>>> solution(5000)
3711
>>> solution(15000)
13255