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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 COMMENTS These are referred to as 'polysticks', 'polyedges' or 'polyforms'. - Jack W Grahl, Jul 24 2018 REFERENCES Brian R. Barwell, "Polysticks," Journal of Recreational Mathematics 22 (1990), 165-175. LINKS D. Goodger, An introduction to Polysticks M. Keller, Counting polyforms D. Knuth, Dancing Links, arXiv:cs/0011047 [cs.DS], 2000. (A discussion of backtracking algorithms which mentions some problems of polystick tiling.) Ed Pegg, Jr., Illustrations of polyforms Eric Weisstein's World of Mathematics, Polyedge [From Eric W. Weisstein, Apr 24 2009] CROSSREFS If only translations (but not rotations) are factored, consider fixed polyedges (A096267). If reflections are considered different, we obtain the one-sided polysticks, counted by (A151537). - Jack W Grahl, Jul 24 2018 Sequence in context: A149972 A026106 A066642 * A137732 A057973 A102461 Adjacent sequences:  A019985 A019986 A019987 * A019989 A019990 A019991 KEYWORD nonn,nice,hard,more AUTHOR EXTENSIONS More terms from Brendan Owen (brendan_owen(AT)yahoo.com), Feb 20 2002 Additional references from Jack W Grahl, Jul 24 2018 STATUS approved

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Last modified October 20 04:37 EDT 2018. Contains 316378 sequences. (Running on oeis4.)