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 A006731 M1055 #20 Oct 04 2019 07:39:58 %S A006731 1,2,4,7,12,20,33,53,85,133,210,322,505,759,1192,1748,2782,3931,6476, %T A006731 8579,15216,17847,36761,33612,93961,47282,262987,-16105,827382, %U A006731 -571524,2936705,-3661626,11507775,-18880652,48169220,-90436605 %N A006731 Site percolation series for square lattice. %D A006731 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006731 I. Jensen, <a href="/A006731/b006731.txt">Table of n, a(n) for n = 0..158</a> (from link below) %H A006731 J. W. Essam, A. J. Guttmann and K. De'Bell, <a href="https://doi.org/10.1088/0305-4470/21/19/018">On two-dimensional directed percolation</a>, J. Phys. A 21 (1988), 3815-3832. %H A006731 Iwan Jensen, <a href="https://researchers.ms.unimelb.edu.au/~ij@unimelb/dirperc/series/sqscs.ser">More terms</a> %H A006731 Iwan Jensen, Anthony J. Guttmann, <a href="https://arxiv.org/abs/cond-mat/9509121">Series expansions of the percolation probability for directed square and honeycomb lattices</a>, arXiv:cond-mat/9509121, 1995; J. Phys. A 28 (1995), no. 17, 4813-4833. %Y A006731 Cf. A056532. %K A006731 sign %O A006731 0,2 %A A006731 _N. J. A. Sloane_, _Simon Plouffe_