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 A054788 #10 Nov 21 2013 13:11:34
%S A054788 0,2,8,4,24,6,40,9,16,56,11,80,13,96,15,112,64,18,136,20,152,22,168,
%T A054788 25,32,184,27,208,29,224,31,240,192,34,264,36,280,38,296,41,48,312,43,
%U A054788 336,45,352,47,368,320,50,392,52,408,54,424,57,72,440,59,464,61,480,63,496
%N A054788 Earliest sequence with a(a(n))=8n.
%H A054788 <a href="/index/Aa#aan">Index entries for sequences of the a(a(n)) = 2n family</a>
%t A054788 nmax = 63; amax = 8*nmax; t = {{0, a[0] = 0}, {1, a[1] = 2}, {2, a[2]}}; While[ !FreeQ[t, a], t = Table[{n, a[n]}, {n, 0, nmax}]; n = Select[t, !IntegerQ[ #[[2]] ] &, 1][[1, 1]]; t2 = Union[ Flatten[ Append[ Select[ t, IntegerQ[ #[[2]] ] &], n]]]; an = If[n == 2, 8, Select[ Complement[ Range[ Max[t2] ], t2], Mod[#, 8] != 0 &, 1][[1]] ]; a[n] = an; While[ an < amax, an = a[n = an] = 8 n]]; Table[ a[n], {n, 0, nmax}] (* _Jean-François Alcover_, Jan 11 2012 *)
%Y A054788 Cf. A002516, A002517, A002518, A007379.
%K A054788 nice,nonn
%O A054788 0,2
%A A054788 _Henry Bottomley_, Apr 27 2000