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The Collatz conjecture states that for any positive integer, repeatedly applying the rule: if even divide by 2, if odd multiply by 3 and add 1 — will always eventually reach 1. It remains one of mathematics' most famous unsolved problems.
公式
If n even: n → n/2; If n odd: n → 3n+1
- n
- positive integer — starting value for the sequence
- s
- stopping time — number of steps to reach 1
ステップバイステップガイド
- 1If n is even: next = n / 2
- 2If n is odd: next = 3n + 1
- 3Continue until reaching 1
- 4The number of steps is called the "stopping time"
解いた例
入力
n = 6
結果
6 → 3 → 10 → 5 → 16 → 8 → 4 → 2 → 1 (8 steps)
入力
n = 27
結果
111 steps, reaches maximum of 9,232
よくある質問
Is the Collatz conjecture proven?
No, it remains one of mathematics' great unsolved problems despite being tested for numbers up to 2⁶⁸.
Why does the Collatz sequence sometimes increase dramatically?
Odd numbers multiply by 3, creating larger values. But many steps follow: divide by 2 repeatedly until odd again.
What is the longest known Collatz stopping time?
For starting values tested, stopping times are in the hundreds. 27 requires 111 steps.
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