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 A289429 #9 Jul 06 2017 16:49:03 %S A289429 1,3,18,126,936,7164,55800,439560,3489696 %N A289429 Sum of factorial-Catalan numbers over a certain family of decorations. %C A289429 The precise definition involves the use of certain symbols akin to the peace symbol. %H A289429 Vincent Pilaud, V. Pons, <a href="http://arxiv.org/abs/1606.09643">Permutrees</a>, arXiv preprint arXiv:1606.09643 [math.CO], 2016. %Y A289429 Cf. A289427, A289428, A289430, A289431. %K A289429 nonn,more %O A289429 0,2 %A A289429 _N. J. A. Sloane_, Jul 06 2017