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 A290722 #35 Nov 24 2017 12:03:35 %S A290722 1,2,4,13,48,238,1325,8297,54519,373363,2621872,18797682,136969519, %T A290722 1011903735,7564219361,57129086391,435394899361,3345082819597, %U A290722 25885718422329,201619294539406,1579629974876090,12442262963919863,98483477967355109,783017782731507416 %N A290722 Number of dissections of a 2n-gon into polygons with even number of sides counted up to rotations and reflections. %H A290722 Andrew Howroyd, <a href="/A290722/b290722.txt">Table of n, a(n) for n = 2..200</a> %H A290722 Evgeniy Krasko, Alexander Omelchenko, <a href="http://www.combinatorics.org/ojs/index.php/eljc/article/view/v22i1p17">Brown's Theorem and its Application for Enumeration of Dissections and Planar Trees</a>, The Electronic Journal of Combinatorics, 22 (2015), #P1.17. %e A290722 For a(4) = 4 the dissections of an octagon are: two dissections into 3 quadrangles; a dissection into one hexagon and one quadrangle; a dissection into one octagon. %o A290722 (PARI) \\ See A295419 for DissectionsModDihedral(). %o A290722 select(v->v>0, DissectionsModDihedral(apply(v->v%2==0, [1..50]))) \\ _Andrew Howroyd_, Nov 22 2017 %Y A290722 Cf. A003168 (counted distinctly). %Y A290722 Cf. A001004, A290816, A295419. %K A290722 nonn %O A290722 2,2 %A A290722 _Evgeniy Krasko_, Sep 03 2017 %E A290722 Terms a(8) and beyond from _Andrew Howroyd_, Nov 22 2017