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 A291418 #5 Feb 16 2025 08:33:50
%S A291418 1,0,-1,0,3,-1,-12,9,55,-67,-267,468,1323,-3180,-6513,21267,30969,
%T A291418 -140581,-135995,919698,494361,-5954217,-829116,38113425,-9433359,
%U A291418 -240844482,154219912,1499076989,-1585801575,-9161079266,13958031252,54710928759,-113373461193,-317030478360,875491422246
%N A291418 Expansion of the series reversion of Sum_{k>=1} x^(k*(k+1)/2).
%C A291418 Reversion of g.f. (with constant term omitted) for A010054.
%H A291418 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>
%H A291418 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SeriesReversion.html">Series Reversion</a>
%H A291418 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A291418 G.f. A(x) satisfies: Sum_{k>=1} A(x)^(k*(k+1)/2) = x.
%t A291418 nmax = 35; Rest[CoefficientList[InverseSeries[Series[Sum[x^(k (k + 1)/2), {k, 1, nmax}], {x, 0, nmax}], x], x]]
%t A291418 nmax = 35; Rest[CoefficientList[InverseSeries[Series[(-2 x^(1/8) + EllipticTheta[2, 0, Sqrt[x]])/(2 x^(1/8)), {x, 0, nmax}], x], x]]
%Y A291418 Cf. A006195, A010054, A179848, A259938.
%K A291418 sign
%O A291418 1,5
%A A291418 _Ilya Gutkovskiy_, Aug 23 2017