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 A095383 #8 Oct 15 2013 22:32:24
%S A095383 0,1,4,6,19,31,73,144,331,672,1468,3024,6065,9592,19701,39630,79625,
%T A095383 157569,316139,632655,1264043,2532963,5060484,10128862,20270752,
%U A095383 40575156,81134041,162268825,324627203,649177198,1298516271,2596827906
%N A095383 Number of different initial values for 3x+1 trajectories started with initial values not exceeding 2^n and in which the peak values are larger than 2^n.
%e A095383 n=4: between iv={1,2,...,16} {7,9,11,13,14,15} provides
%e A095383 peak values larger than 16, so a[4]=6.
%t A095383 c[x_]:=c[x]=(1-Mod[x, 2])*(x/2)+Mod[x, 2]*(3*x+1);c[1]=1; fpl[x_]:=FixedPointList[c, x]; {$RecursionLimit=1000;m=0}; Table[Print[{xm-1, m}];m=0; Do[If[Greater[Max[fpl[n]], 2^xm], m=m+1], {n, 1, 2^xm}], {xm, 1, 30}]
%Y A095383 Cf. A087256, A095381, A095382, A095384.
%K A095383 nonn
%O A095383 1,3
%A A095383 _Labos Elemer_, Jun 14 2004
%E A095383 a(22)-a(32) from _Donovan Johnson_, Feb 02 2011