cp's OEIS Frontend

A332454 Starting from sigma(n)+1, number of halving steps to reach 1 in '3x+1' problem, or -1 if this never happens.

%I A332454 #7 Feb 16 2020 17:36:09
%S A332454 1,2,4,3,11,7,13,4,12,14,7,13,12,16,16,5,14,7,6,20,18,15,16,14,5,20,
%T A332454 69,22,67,73,18,6,17,71,17,13,23,14,22,59,20,75,12,8,24,73,17,69,14,
%U A332454 67,73,18,71,61,73,61,16,59,14,33,68,75,26,7,8,74,11,31,75,74,73,19,11,23,69,12,75,33,16,30,15,31,8,35,72,20
%N A332454 Starting from sigma(n)+1, number of halving steps to reach 1 in '3x+1' problem, or -1 if this never happens.
%H A332454 Antti Karttunen, <a href="/A332454/b332454.txt">Table of n, a(n) for n = 1..16384</a>
%H A332454 Antti Karttunen, <a href="/A332454/a332454.txt">Data supplement: n, a(n) computed for n = 1..65537</a>
%H A332454 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>
%H A332454 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F A332454 a(n) = A006666(A088580(n)) = A006666(1+sigma(n)).
%o A332454 (PARI)
%o A332454 A006666(n) = { my(t=0); while(n>1, if(n%2, n=3*n+1, n>>=1; t++)); (t); }; \\ From A006666
%o A332454 A332454(n) = A006666(1+sigma(n));
%Y A332454 Cf. A000203, A006666, A088580, A332452, A332455.
%Y A332454 Cf. also A324294.
%K A332454 nonn
%O A332454 1,2
%A A332454 _Antti Karttunen_, Feb 16 2020