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 A050391 #17 Apr 22 2020 07:59:25
%S A050391 1,-1,0,3,-8,12,-6,-37,208,-730,1708,-1278,-10018,56782,-163644,
%T A050391 229985,389830,-3724538,13460550,-28799694,12470564,205544596,
%U A050391 -1084748334,3195484242,-4851317704,-7421547798,81343472008
%N A050391 Reversion of Euler totient function A000010.
%H A050391 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>
%H A050391 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A050391 G.f. A(x) satisfies: A(x) = x - Sum_{k>=2} phi(k) * A(x)^k. - _Ilya Gutkovskiy_, Apr 22 2020
%o A050391 (PARI) Vec(serreverse(sum(n=1, 50, moebius(n)*x^n/(1-x^n)^2 + O(x^50)))) \\ _Michel Marcus_, Sep 25 2017
%Y A050391 Cf. A000010, A050392.
%K A050391 sign
%O A050391 1,4
%A A050391 _Christian G. Bower_, Nov 15 1999