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 A334262 #10 Apr 21 2020 08:43:27
%S A334262 1,-3,21,-235,3630,-71631,1721671,-48804183,1594177605,-58963348675,
%T A334262 2435865852156,-111169287046467,5554808694622369,-301609325982387255,
%U A334262 17682700497003095625,-1113293610926803531951,74915504280675843548274,-5365793673423031533999147
%N A334262 E.g.f. A(x) satisfies: A(x) = 2 * x / (exp(A(x)) * (2 + A(x))).
%C A334262 Exponential reversion of A000217 (triangular numbers).
%H A334262 Vaclav Kotesovec, <a href="/A334262/b334262.txt">Table of n, a(n) for n = 1..200</a>
%H A334262 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A334262 a(n) ~ -(-1)^n * n^(n-1) / (2^(1/4) * (sqrt(2)-1)^(n - 1/2) * exp(n*(sqrt(2)-1))). - _Vaclav Kotesovec_, Apr 21 2020
%t A334262 nmax = 18; CoefficientList[InverseSeries[Series[Exp[x] (x + x^2/2), {x, 0, nmax}], x], x] Range[0, nmax]! // Rest
%o A334262 (PARI) seq(n)= Vec(serlaplace(serreverse(sum(k=1, n, (k*(k+1)/2)*x^k/k!) + O(x*x^n)))); \\ _Michel Marcus_, Apr 21 2020
%Y A334262 Cf. A000217, A066399, A179848.
%K A334262 sign
%O A334262 1,2
%A A334262 _Ilya Gutkovskiy_, Apr 20 2020