A287319 Smallest number k which becomes a power of 2 after being transformed by the reduced Collatz function k=(3*k+1)/2 precisely n times.

1, 3, 151, 26512143, 318400215865581346424671, 1240913164837493520914469575281720548839055905624577375251388717505927743

Offset

1,2

Comments

a(7) is too large to include.

I conjecture that all members of a(n) are members of A054646 and A010120, "Smallest number to give 2^(2n) in a hailstone (3x + 1) sequence" and "Smallest start for a `3x+1' sequence containing 2^n".

Links

Table of n, a(n) for n=1..6.

Formula

a(n) = ((2^(3^(n-1)+n)-3^n+2^n))/3^n.

Example

For n = 3, the reduced Collatz sequence k = (3*k+1)/2 is 151, 227, 341, 512.

Crossrefs

Cf. A054646 and A010120.

Sequence in context: A157578 A137802 A100203 * A189248 A209393 A095225

Adjacent sequences: A287316 A287317 A287318 * A287320 A287321 A287322

Keyword

nonn

Author

Joe Slater, May 23 2017

Status

approved