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 A121788 #9 Jan 10 2019 22:39:31 %S A121788 2,2,32,104,10180,111712,67590888,2688307514,9628765945000, %T A121788 1445778936756068,29725924602729604016,17337631013706758184626, %U A121788 1998903003325610328086958408,4628650743368437273677525554148 %N A121788 "Crossing Hamiltonian walks" on the square lattice (see Jensen web site for further information). %H A121788 I. Jensen, <a href="/A121788/b121788.txt">Table of n, a(n) for n = 1..17</a> [from the Jensen link below] %H A121788 I. Jensen, <a href="https://web.archive.org/web/20070612141707/http://www.ms.unimelb.edu.au/~iwan/saw/SAW_ser.html">Series Expansions for Self-Avoiding Walks</a> %H A121788 I. Jensen, <a href="https://web.archive.org/web/20070613021747/http://www.ms.unimelb.edu.au/~iwan/saw/series/hami_cross.ser">Crossing Hamiltonian walks</a> %K A121788 nonn %O A121788 1,1 %A A121788 _N. J. A. Sloane_, Aug 30 2006