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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.

Formula

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

Guida passo passo

  1. 1If n is even: next = n / 2
  2. 2If n is odd: next = 3n + 1
  3. 3Continue until reaching 1
  4. 4The number of steps is called the "stopping time"

Esempi risolti

Ingresso
n = 6
Risultato
6 → 3 → 10 → 5 → 16 → 8 → 4 → 2 → 1 (8 steps)
Ingresso
n = 27
Risultato
111 steps, reaches maximum of 9,232

Domande frequenti

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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