%I M2742 #13 Mar 30 2012 18:36:10
%S 1,0,-1,-3,-8,-21,-56,-154,-434,-1252,-3675,-10954,-33044,-100676,
%T -309569,-957424,-2987846,-9330274,-29522921,-92459524,-298142956,
%U -922424269,-3098690837,-9042937179,-34187149573,-79544646085
%N Percolation series for directed square lattice.
%D K. De'Bell and J. W. Essam, Estimates of the site percolation probability exponents for some directed lattices, J. Phys. A 16 (1983), 3145-3147.
%D Iwan Jensen and Anthony J. Guttmann, Series Expansions of the Percolation Probability for Directed Square and Honeycomb Lattices, J. Phys. A 28 (1995), 4813-4833.
%D R. N. Onody and U. P. C. Neves, Series Expansion of the Directed Percolation Probability, J. Phys. A 25 (1992), 6609-6615.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H I. Jensen, <a href="/A006835/b006835.txt">Table of n, a(n) for n = 0..37</a> (from link below)
%H I. Jensen, <a href="http://www.ms.unimelb.edu.au/~iwan/dirperc/series/sqspp.ser">More terms</a>
%K sign
%O 0,4
%A _N. J. A. Sloane_ and _Simon Plouffe_