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 A096890 #6 Nov 25 2013 12:59:03
%S A096890 401408,414050,436032,455625,462400,466608,476100,486300,486900,
%T A096890 512337,522242,526974,543600,544644,544944,546192,546861,554304,
%U A096890 559504,571536,572313,575028,577200,579856,583200,585528,599694,604300,609429,611618
%N A096890 Initial values for f(x)=phi(sigma(x)) such that iteration of f ends in a cycle of length 18.
%H A096890 Charles R Greathouse IV, <a href="/A096890/b096890.txt">Table of n, a(n) for n = 1..10000</a>
%t A096890 g[n_] := EulerPhi[ DivisorSigma[1, n]]; f[n_] := f[n] = Block[{lst = NestWhileList[g, n, UnsameQ, All ]}, -Subtract @@ Flatten[ Position[lst, lst[[ -1]]]]]; Select[ Range[624900], f[ # ] == 18 &]
%o A096890 (PARI) f(x)=eulerphi(sigma(x))
%o A096890 is(n)=my(t=f(n), h=f(t)); while(t!=h, t=f(t); h=f(f(h))); for(i=1,17,h=f(h); if(t==h,return(0))); t==f(h) \\ _Charles R Greathouse IV_, Nov 25 2013
%Y A096890 Cf. A000010, A000203, A095952, A096887, A095953, A096526, A095954, A096888, A096889, A095955, A095956.
%K A096890 nonn
%O A096890 1,1
%A A096890 _Labos Elemer_ and _Robert G. Wilson v_, Jul 14 2004