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 A050397 #19 May 06 2023 23:07:59 %S A050397 1,-2,4,-10,30,-104,392,-1568,6520,-27976,122944,-551680,2518912, %T A050397 -11684000,54957216,-261897024,1263216192,-6164172608,30416619200, %U A050397 -151750104800,765364073120,-3902783995520,20123276097920 %N A050397 Reversion of sequence of involutions (A000085). %H A050397 Andrew Howroyd, <a href="/A050397/b050397.txt">Table of n, a(n) for n = 1..200</a> %H A050397 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a> %H A050397 <a href="/index/Res#revert">Index entries for reversions of series</a> %p A050397 # Using function CompInv from A357588. %p A050397 CompInv(23, n -> simplify(hypergeom([-n/2, (1-n)/2], [], 2))); # _Peter Luschny_, Oct 05 2022 %o A050397 (PARI) seq(n)=Vec(serreverse(serlaplace(-1 + exp(x+x^2/2 + O(x*x^n))))) \\ _Andrew Howroyd_, May 06 2023 %Y A050397 Cf. A000085, A050398. %K A050397 sign %O A050397 1,2 %A A050397 _Christian G. Bower_, Nov 15 1999