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 A006782 M1930 #43 May 06 2025 11:05:58 %S A006782 1,0,1,2,9,36,154,684,3128,14666,70258,342766,1698625,8532410, %T A006782 43368153,222729492,1154455161,6033034032,31760434883,168311948410, %U A006782 897327111964,4810159375532,25914118276362 %N A006782 Number of polygons of length 4n on L-lattice. %D A006782 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006782 Thorsten Ehlers, <a href="/A006782/a006782_1.c.txt">(C) simple generation algorithm</a> %H A006782 I. G. Enting and A. J. Guttmann, <a href="https://doi.org/10.1088/0305-4470/18/6/022">Self-avoiding polygons on the square, L and Manhattan lattices</a>, J. Phys. A 18 (1985), 1007-1017. %H A006782 Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a006/A006782.java">Java program</a> (github) %Y A006782 Cf. A002931, A006781. %K A006782 nonn,more %O A006782 1,4 %A A006782 _N. J. A. Sloane_ %E A006782 a(13)-a(15) from _Sean A. Irvine_, Aug 01 2017 %E A006782 a(16)-a(21) from _Thorsten Ehlers_, Sep 30 2018 %E A006782 a(22) from _Thorsten Ehlers_, Nov 01 2018 %E A006782 a(23) from _Thorsten Ehlers_, Apr 16 2019