

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



