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 A216818 #12 Oct 10 2023 09:46:00 %S A216818 1,0,2,4,12,32,110,340,1193,4080,14786,53428 %N A216818 Number of simply 4-connected polyominoes of site-perimeter n. %H A216818 J. Fortier, A. Goupil, J. Lortie and J. Tremblay, <a href="https://doi.org/10.1016/j.tcs.2012.02.032">Exhaustive generation of gominoes</a>, Theoretical Computer Science, 502 (2013), 76-87. %K A216818 nonn,more %O A216818 4,3 %A A216818 _N. J. A. Sloane_, Sep 20 2012