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 A006813 M2778 #16 Jul 08 2025 16:56:00 %S A006813 3,9,21,48,105,219,459,936 %N A006813 Percolation series for directed hexagonal lattice. %C A006813 The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice. %D A006813 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006813 J. Blease, <a href="https://doi.org/10.1088/0022-3719/10/7/003">Series expansions for the directed-bond percolation problem</a>, J. Phys C vol 10 no 7 (1977), 917-924. %H A006813 G. Nebe and N. J. A. Sloane, <a href="http://www.math.rwth-aachen.de/~Gabriele.Nebe/LATTICES/A2.html">Home page for hexagonal (or triangular) lattice A2</a> %K A006813 nonn,more %O A006813 1,1 %A A006813 _N. J. A. Sloane_