This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A081613 #8 Nov 21 2013 12:47:59
%S A081613 1,1,2,9,11,21,21,42,45,87,67,148,211,176,265,256,260,427,426,363,388,
%T A081613 501,490,448,450,390,560,420,518,634,445,530,535,796,951,827,814,1070,
%U A081613 690,729,786,910,820,1014,1172,1219,997,1328,1331,892,1296
%N A081613 Length of iteration list when Collatz-function is iterated with initial value n!=A000142[n].
%F A081613 a(n)=A008908(A000142(n))
%e A081613 n = 6: list = {720, 360, 180, 90, 45, 136, 68, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1 }
%t A081613 f[x_] := (1-Mod[x, 2])*(x/2)+(Mod[x, 2])*(3*x+1) f[1]=1; f0[x_] := FixedPointList[f, x] le[x_] := Length[FixedPointList[f, x]]-1 Table[le[w! ], {w, 1, 50}]
%t A081613 Table[Length[NestWhileList[If[EvenQ[#],#/2,3#+1]&,n!,#!=1&]],{n,0,50}] (* _Harvey P. Dale_, Apr 08 2012 *)
%Y A081613 Cf. A006370, A008908, A074472, A075484-A075488, A000142.
%K A081613 nonn
%O A081613 0,3
%A A081613 _Labos Elemer_, Apr 17 2003