cp's OEIS Frontend

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).

%I A076138 #8 Mar 22 2025 19:22:58
%S A076138 1,4,5,6,11,14,15,16,18,19,20,21,24,25,26,27,33,34,35,43,44,45,46,47,
%T A076138 56,57,58,59,60,61,62,63,64,72,74,76,77,78,79,80,81,82,83,84,85,96,98,
%U A076138 99,100,101,102,103,104,105,106,107,108,109,110,113,130,131,132,133,134,135
%N 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).
%C A076138 a(n) seems to be asymptotic to 2*n and a(n)=2*n for some n (5, 14, 43, 54, 72, 93, ...)
%C A076138 Positions of 1's in A006513. - _Sean A. Irvine_, Mar 21 2025
%F A076138 a(n+1) = min (k>a(n) : A076057(k)=A076057(a(n))).
%Y A076138 Cf. A006513, A076057.
%K A076138 nonn
%O A076138 1,2
%A A076138 _Benoit Cloitre_, Oct 31 2002
%E A076138 Missing 16 and 18 inserted by _Sean A. Irvine_, Mar 21 2025