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A019988
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Number of ways of embedding a connected graph with n edges in the square lattice.
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4
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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)
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OFFSET
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1,2
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LINKS
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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]
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CROSSREFS
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Sequence in context: A149972 A026106 A066642 * A137732 A057973 A102461
Adjacent sequences: A019985 A019986 A019987 * A019989 A019990 A019991
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KEYWORD
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nonn,nice,hard,more
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AUTHOR
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Russ Cox
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EXTENSIONS
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More terms from Brendan Owen (brendan_owen(AT)yahoo.com), Feb 20 2002
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STATUS
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approved
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