A076138 a(1)=1; a(n+1) is the smallest integer > a(n) such that C_2k(a(n+1))=C_2k(a(n)) for k large enough, where C_m(n) is the modified Collatz map iterated m times on n ( x->x/2 if x is even x->(3x+1)/2 if x is odd).

1, 4, 5, 6, 11, 14, 15, 16, 18, 19, 20, 21, 24, 25, 26, 27, 33, 34, 35, 43, 44, 45, 46, 47, 56, 57, 58, 59, 60, 61, 62, 63, 64, 72, 74, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 96, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 113, 130, 131, 132, 133, 134, 135

Offset

1,2

Comments

a(n) seems to be asymptotic to 2*n and a(n)=2*n for some n (5, 14, 43, 54, 72, 93, ...)

Positions of 1's in A006513. - Sean A. Irvine, Mar 21 2025

Links

Table of n, a(n) for n=1..66.

Formula

a(n+1) = min (k>a(n) : A076057(k)=A076057(a(n))).

Crossrefs

Cf. A006513, A076057.

Sequence in context: A284513 A047311 A224081 * A347269 A316783 A050037

Adjacent sequences: A076135 A076136 A076137 * A076139 A076140 A076141

Keyword

nonn

Author

Benoit Cloitre, Oct 31 2002

Extensions

Missing 16 and 18 inserted by Sean A. Irvine, Mar 21 2025

Status

approved