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 A097001 #4 Oct 15 2013 22:32:33
%S A097001 2,4,12,16,72,252,312,256,1512,1860,12264,6552,26208,34200,93600,
%T A097001 65536,833280,1116024,2239920,4464096,9865440,8124480,569540160,
%U A097001 569540160,1100946774480,1100946774480,1100946774480,1100946774480,34696672920
%N A097001 A062402(x)=sigma(phi[x]) function is iterated; initial value=2^n; a(n)=largest term of trajectory.
%e A097001 n=13: 2^n=8192, list={8192,8191,26208,[20440],20440,.. a[13]=26208 arose in transient.
%t A097001 gf[x_] :=DivisorSigma[1, EulerPhi[x]] gite[x_, hos_] :=NestList[gf, x, hos] Table[Max[gite[2^w, 200]], {w, 1, 30}]
%Y A097001 Cf. A000010, A000203, A062402, A096852.
%K A097001 nonn
%O A097001 1,1
%A A097001 _Labos Elemer_, Jul 21 2004