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 A128021 #9 Oct 10 2019 11:21:34
%S A128021 1,1,2,3,5,8,14,25,44,79,144,264,487,905,1689,3167,5962,11261,21337,
%T A128021 40540,77219,147418,282017,540533,1037823,1995814,3843790,7413023,
%U A128021 14314803,27675286,53565070,103782323,201274808,390709922,759093562
%N A128021 a(n) = A128020(n)/n.
%F A128021 a(n) = 1 + floor(sum{k=1 to n-1} A128020(k) /n).
%t A128021 f[l_List] := Block[{n = Length[l] + 1},Append[l, (1 + Floor[Sum[k*l[[k]], {k, n - 1}]/n])]];Nest[f, {}, 37] (* _Ray Chandler_, Feb 12 2007 *)
%Y A128021 Cf. A128020.
%K A128021 easy,nonn
%O A128021 1,3
%A A128021 _Leroy Quet_, Feb 11 2007
%E A128021 Extended by _Ray Chandler_, Feb 12 2007