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 A082398 #3 Mar 31 2012 21:03:39
%S A082398 1,0,3,10,33,106,331,1009,3017,8884,25841,74416,212533,602785,1699503,
%T A082398 4767166,13312641,37031254,102651967,283676689,781763381,2149017256,
%U A082398 5894114513,16132400860,44071485673,120188174401,327242994651
%N A082398 Number of directed, diagonally convex polyominoes with n cells.
%D A082398 Fouad Ibn-Majdoub-Hassani. Combinatoire de polyominos et des tableaux decales oscillants. These de Doctorat, Laboratoire de Recherche en Informatique, Universite Paris-Sud XI, France.
%F A082398 G.f.: (x*(1-4*x+6*x^2-3*x^3+x^4))/((1-x)*(1-3*x+x^2)^2)
%t A082398 Join[{1, 0}, Take[CoefficientList[Series[(q*(1 - 4*q + 6*q^2 - 3*q^3 + q^4))/((1 - q)*(1 - 3*q + q^2)^2), {q, 0, 27}], q], -26]]
%K A082398 nonn,easy
%O A082398 1,3
%A A082398 _Fouad IBN MAJDOUB HASSANI_, Apr 14 2003
%E A082398 More terms from _Robert G. Wilson v_, Apr 15 2003