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 A113900 #13 Apr 16 2016 12:04:53 %S A113900 1,6,255,92263,281035054,7490694495750,1789509008288411290 %N A113900 Number of partitions of 2n X 2n checkerboard into two congruent edgewise-connected sets, counting partitions equal under rotation or reflection only once. %D A113900 Howard Eves, A Survey of Geometry, 1963, p265. %H A113900 Giovanni Resta, <a href="/A113900/a113900.pdf">Illustrations for a(2) = 6 and a(3) = 255</a>. %e A113900 All partitions are radially symmetric, hence can be identified by half the cut. The solution for 4 X 4 follows, with coordinates of starting point and direction of each subsequent incremental cut (North is positive Y). %e A113900 (1,0)NNNES (1,0)NNE (1,0)NEN (1,0)NEENW (2,0)NN (2,0)NENW total = 6 %Y A113900 Cf. A064941, A068392, A257952. %K A113900 nonn,more %O A113900 1,2 %A A113900 Joseph Sardinha (jsardi3(AT)juno.com), Jan 29 2006 %E A113900 a(5) corrected by _Giovanni Resta_, May 14 2015 %E A113900 New value of a(5) confirmed by and additional values a(6) and a(7) from _Andrew Howroyd_, Apr 13 2016