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 A222202 #20 Jan 01 2019 06:31:06 %S A222202 1,18,13903,360783593,303872744726644,8217125138015950451626, %T A222202 7095967027221343377167292602835, %U A222202 195081705501438193439250404333039349462635,170400931523966165754313513175663906434875251822099185,4722705723996809689481769489662532396060449405036901391459114641198 %N A222202 Number of ways to cover the 2n X 2n grid graph by vertex disjoint cycles. %H A222202 Andrew Howroyd, <a href="/A222202/b222202.txt">Table of n, a(n) for n = 1..12</a> %H A222202 Peter Tittmann, <a href="http://web.archive.org/web/20070715034048/http://www.htwm.de/~peter/research/enumeration.html">Enumeration in graphs: counting Hamiltonian cycles</a> [Archived link] %Y A222202 Cf. A222203, A222204. %K A222202 nonn %O A222202 1,2 %A A222202 _N. J. A. Sloane_, Feb 14 2013 %E A222202 a(10)-a(12) from _Andrew Howroyd_, Nov 16 2015