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 A196991 #10 Feb 16 2025 08:33:15 %S A196991 4,10,32,112,412,1572,6148,24494,98992,404650,1669496,6941226, %T A196991 29047568,122235518,516860460,2194691988,9353657788 %N A196991 Number of fixed polycairos with n cells. %H A196991 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Polycairo.html">Polycairo</a> %Y A196991 Cf. A151534, A151535, A151536, A159866. %K A196991 nonn,hard %O A196991 1,1 %A A196991 _Joseph Myers_, Oct 08 2011 %E A196991 a(16)-a(17) from _Johann Peters_, Aug 05 2024