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 A231690 #34 Oct 24 2018 03:37:04
%S A231690 1,6,56,640,8158,111258,1588544,23446248,354855218,5477342222,
%T A231690 85893429256,1364577254040,21916000458014,355251287893170,
%U A231690 5804407209709312,95493879511032240,1580592247322440642,26301843121772151254,439764358275666481496,7384252698468635017936,124469446338979722639294
%N A231690 Cardinalities of the sub-operad FF_6 of the operad MFF.
%H A231690 Gheorghe Coserea, <a href="/A231690/b231690.txt">Table of n, a(n) for n = 1..301</a>
%H A231690 F. Chapoton, F. Hivert, J.-C. Novelli, <a href="http://arxiv.org/abs/1307.0092">A set-operad of formal fractions and dendriform-like sub-operads</a>, arXiv preprint arXiv:1307.0092 [math.CO], 2013.
%F A231690 A(x) = serreverse(A213667(-x))(-x). - _Gheorghe Coserea_, Jan 13 2017
%t A231690 InverseSeries[x(1 - 3x - x^2 + x^3)/(1 + 3x + x^2 - x^3) + O[x]^22] // CoefficientList[#, x]& // Rest (* _Jean-François Alcover_, Oct 24 2018, from PARI *)
%o A231690 (PARI) N=22; x='x+O('x^N);
%o A231690 Vec(serreverse(Ser(x*(1-3*x-x^2+x^3)/(1+3*x+x^2-x^3)))) \\ _Gheorghe Coserea_, Jan 13 2017
%Y A231690 Cf. A213667, A231691.
%K A231690 nonn
%O A231690 1,2
%A A231690 _N. J. A. Sloane_, Nov 14 2013
%E A231690 Offset changed and more terms from _Gheorghe Coserea_, Jan 13 2017