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 A057410 #6 Mar 30 2012 16:48:52 %S A057410 1,12,94,604,3463,18440,93274,454412,2151673,9964500,45335002, %T A057410 203303760,900901387,3952468348,17194102478,74257185512,318693463933, %U A057410 1360298775524,5778468266446,24442845038580 %N A057410 Number of staircase polygons of perimeter 2n with one (staircase polygon) hole on square lattice (not allowing rotations). %H A057410 I. Jensen, <a href="/A057410/b057410.txt">Table of n, a(n) for n = 8..103</a> (from link below) %H A057410 I. Jensen, <a href="http://www.ms.unimelb.edu.au/~iwan/polygons/series/staircase.perim.1hole.ser">More terms</a> %K A057410 nonn %O A057410 8,2 %A A057410 _N. J. A. Sloane_, Aug 30 2000, corrected Aug 29 2006