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 A302657 #20 Apr 12 2018 05:15:31
%S A302657 1,1,4,66,2576,181580,20040132,3176873014,683004260416,
%T A302657 191131280146584,67496202291859460,29358012892996082966,
%U A302657 15422766301341408798384,9628365732822661693594804,7046590639669984518105404260,5975695685335003337179698967230,5813189543201787075970895280603392
%N A302657 a(n) = [x^n] 1 + x*(1 + 2*x*(1 + 3*x*(1 + 4*x*(1 + 5*x*(1 + ...)^n)^n)^n)^n)^n.
%C A302657 (a(n) / (n-1)!^2)^(1/n) tends to 4.3002... - _Vaclav Kotesovec_, Apr 11 2018
%H A302657 Vaclav Kotesovec, <a href="/A302657/b302657.txt">Table of n, a(n) for n = 0..100</a>
%t A302657 Table[SeriesCoefficient[1 + x Fold[((#2 + 1) x #1 + 1)^n &, 0, Reverse[Range[n]]], {x, 0, n}], {n, 0, 16}]
%Y A302657 Cf. A000142, A128318, A128319, A302686.
%K A302657 nonn
%O A302657 0,3
%A A302657 _Ilya Gutkovskiy_, Apr 11 2018