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 A273988 #21 Jul 02 2016 02:26:19
%S A273988 1,2,6,19,78,387,2327,16384,132336,1203145,12146959,134749221,
%T A273988 1628840129,21308361378,299940041508,4520381905248,72625922986869,
%U A273988 1239160455312246,22377511072312218,426411855436193451,8550614540544797370,179989316790109543775,3968315581691624472787,91451247683519227059456
%N A273988 The number of slim, rectangular lattices of length n>=2.
%C A273988 The initial term is the four element diamond shape lattice.
%H A273988 Vaclav Kotesovec, <a href="/A273988/b273988.txt">Table of n, a(n) for n = 2..400</a>
%H A273988 Gábor Czédli, Tamás Dékány, Gergő Gyenizse, Júlia Kulin, <a href="http://dx.doi.org/10.1007/s00012-015-0363-y">The number of slim rectangular lattices</a>, Algebra Universalis, 2016, Volume 75, Issue 1, pp 33-50
%F A273988 a(n) = 1/2*( A273596(n) + Sum_{k=1..floor(n/2)} binomial(n-k-1,k-1)*A000085(n-2k) ).
%F A273988 a(n) ~ exp(2) * n! / (2*n^2). - _Vaclav Kotesovec_, Jun 30 2016
%Y A273988 Cf. A000085, A273596.
%K A273988 nonn
%O A273988 2,2
%A A273988 _Tamas Dekany_, Jun 06 2016