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 A053512 #19 Dec 04 2018 23:28:46 %S A053512 1,6,92,4256,631408,287890282,394680026626,1633299243490821, %T A053512 20522104351316248402,784379015232375006607050, %U A053512 91206645757124024620735442618,32264019671635009481678592579241059,34725332380760680832137350774453679498244 %N A053512 Half the number of non-self-intersecting paths from one corner of an n X n grid to the opposite corner. %F A053512 a(n) = A007764(n) / 2. - _Andrew Howroyd_, May 12 2017 %Y A053512 Cf. A007764. %K A053512 nonn,walk %O A053512 2,2 %A A053512 _Horst H. Manninger_, Jan 14 2000 %E A053512 Corrected, additional terms from A007764 by _Andrew Howroyd_, May 12 2017 %E A053512 Offset corrected by _Joerg Arndt_, Dec 03 2018