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A019988 Number of ways of embedding a connected graph with n edges in the square lattice. 4
1, 2, 5, 16, 55, 222, 950, 4265, 19591, 91678, 434005, 2073783, 9979772, 48315186, 235088794, 1148891118, 5636168859 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..17.

Ed Pegg, Jr., Illustrations of polyforms

M. Keller, Counting polyforms

Eric Weisstein's World of Mathematics, Polyedge [From Eric W. Weisstein, Apr 24 2009]

CROSSREFS

Sequence in context: A149972 A026106 A066642 * A137732 A057973 A102461

Adjacent sequences:  A019985 A019986 A019987 * A019989 A019990 A019991

KEYWORD

nonn,nice,hard,more

AUTHOR

Russ Cox

EXTENSIONS

More terms from Brendan Owen (brendan_owen(AT)yahoo.com), Feb 20 2002

STATUS

approved

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Last modified October 24 14:47 EDT 2014. Contains 248516 sequences.