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 A067968 #16 Sep 26 2024 18:49:40 %S A067968 1,2,11,163,6547,720417,216173426,177509416175,398239490006383, %T A067968 2441922679051541299,40923800121824894177005, %U A067968 1874434223405139511637099884,234647514833189124245764389957097,80281172893810827268371440460572492150 %N A067968 Number of binary arrangements on n X n array without adjacent three 1's. %D A067968 Steven R. Finch, Mathematical Constants, Cambridge, 2003, pp. 342-349. %H A067968 Steven R. Finch, <a href="http://www.people.fas.harvard.edu/~sfinch/constant/square/square.html">Hard Square Entropy Constant</a> [Broken link] %H A067968 Steven R. Finch, <a href="http://web.archive.org/web/20010605012506/http://www.mathsoft.com/asolve/constant/square/square.html">Hard Square Entropy Constant</a> [From the Wayback machine] %Y A067968 Adjacent three in a row or column gives A050974. %K A067968 nonn %O A067968 0,2 %A A067968 _R. H. Hardin_, Feb 02 2002 %E A067968 a(13) from _Sean A. Irvine_, Jan 15 2024 %E A067968 a(0)=1 prepended by _Alois P. Heinz_, Sep 26 2024