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 A054787 #11 Aug 28 2016 18:23:40
%S A054787 0,2,7,4,21,6,35,14,9,56,11,70,13,84,49,16,105,18,119,20,133,28,23,
%T A054787 154,25,168,27,182,147,30,203,32,217,34,231,42,37,252,39,266,41,280,
%U A054787 245,44,301,46,315,48,329,98,51,350,53,364,55,378,63,58,399,60,413,62,427,392
%N A054787 Earliest sequence with a(a(n))=7n.
%H A054787 T. D. Noe, <a href="/A054787/b054787.txt">Table of n, a(n) for n = 0..1000</a>
%H A054787 <a href="/index/Aa#aan">Index entries for sequences of the a(a(n)) = 2n family</a>
%F A054787 a(7n)=7*a(n), a(7n+1)=7n+2, a(7n+2)=49n+7, a(7n+3)=7n+4, a(7n+4)=49n+21, a(7n+5)=7n+6, a(7n+6)=49n+35
%t A054787 a[n_] := a[n] = Which[ Mod[n, 7] == 0, 7*a[n/7], Mod[n, 7] == 1, n+1, Mod[n, 7] == 2, 7*(n-2)+7, Mod[n, 7] == 3, n+1, Mod[n, 7] == 4, 7*(n-4)+21, Mod[n, 7] == 5, n+1, Mod[n, 7] == 6, 7*(n-6)+35]; a[0] = 0; Table[a[n], {n, 0, 63}] (* _Jean-François Alcover_, Sep 24 2012 *)
%Y A054787 Cf. A002516, A002517, A002518, A007379.
%K A054787 nice,nonn
%O A054787 0,2
%A A054787 _Henry Bottomley_, Apr 27 2000