cp's OEIS Frontend

A332455 Starting from sigma(n)+1, number of tripling steps to reach 1 in '3x+1' problem, or -1 if 1 is never reached.

%I A332455 #11 Feb 16 2020 17:36:16
%S A332455 0,0,1,0,5,2,6,0,5,6,2,5,5,7,7,0,6,1,1,9,8,6,7,5,0,9,40,10,39,42,8,0,
%T A332455 7,41,7,4,11,5,10,33,9,43,4,1,11,42,7,39,5,38,42,7,41,34,42,34,6,33,5,
%U A332455 16,39,43,12,0,1,42,3,15,43,42,42,7,3,10,39,3,43,16,6,14,5,15,1,17,41,8,34,4,33,46,2,16,44,42,34,39
%N A332455 Starting from sigma(n)+1, number of tripling steps to reach 1 in '3x+1' problem, or -1 if 1 is never reached.
%H A332455 Antti Karttunen, <a href="/A332455/b332455.txt">Table of n, a(n) for n = 1..16384</a>
%H A332455 Antti Karttunen, <a href="/A332455/a332455.txt">Data supplement: n, a(n) computed for n = 1..65537</a>
%H A332455 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>
%H A332455 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F A332455 a(n) = A006667(A088580(n)) = A006667(1+sigma(n)).
%F A332455 a(2^n) = 0 for all n >= 0. [Zero occurs at least also at a(25). See A202274]
%o A332455 (PARI)
%o A332455 A006667(n) = { my(t=0); while(n>1, if(n%2, t++; n=3*n+1, n>>=1)); (t); };
%o A332455 A332455(n) = A006667(1+sigma(n));
%Y A332455 Cf. A000203, A006667, A088580, A202274, A332453, A332454.
%Y A332455 Cf. also A324294, A332459.
%K A332455 nonn
%O A332455 1,5
%A A332455 _Antti Karttunen_, Feb 16 2020