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URL: https://oeis.org/A006809

⇱ A006809 - OEIS

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A006809
Bond percolation series for hexagonal lattice.
7
1, 3, 9, 25, 66, 168, 417, 1014, 2427, 5737, 13412, 31088, 71506, 163378, 371272, 839248, 1889019, 4235082, 9459687, 21067566, 46769977, 103574916, 228808544, 504286803, 1109344029, 2435398781, 5337497418, 11678931098
OFFSET
0,2
COMMENTS
The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice.
The first negative term occurs at index 89.
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
I. Jensen, Table of n, a(n) for n = 0..90 (from link below)
J. Blease, Series expansions for the directed-bond percolation problem, J. Phys. C 10 (1977), 917-924.
J. W. Essam, A. J. Guttmann and K. De'Bell, On two-dimensional directed percolation, J. Phys. A 21 (1988), 3815-3832.
I. Jensen, More terms
Iwan Jensen, Anthony J. Guttmann, Series expansions of the percolation probability for directed square and honeycomb lattices, J. Phys. A 28 (1995), no. 17, 4813-4833.
CROSSREFS
Sequence in context: A335472 A096322 A058396 * A081663 A245748 A181383
KEYWORD
sign
STATUS
approved