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A005768
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Number of convex polygons of length 2n on square lattice whose left-most bottom vertex is strictly to the left of the right-most top vertex.
(Formerly M1776)
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3
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1, 2, 7, 27, 110, 460, 1948, 8296, 35400, 151056, 643892, 2740216, 11639416, 49340080, 208727176, 881212272, 3713043152, 15615663008, 65555425780
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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REFERENCES
| M.-P. Delest and G. Viennot, Algebraic languages and polyominoes enumeration, Theoretical Computer Sci., 34 (1984), 169-206.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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FORMULA
| G.f. x^2*(1-8*x+21*x^2-19*x^3+4*x^4)/((1-2*x^(1/2))^2*(1+2*x^(1/2))^2*(1-2*x)) - 2*x^4*(1-4*x)^(-3/2) - Markus Voege (voege(AT)blagny.inria.fr), Nov 28 2003
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CROSSREFS
| A005436(n) = a(n) + A005769(n) + A005770(n)
Sequence in context: A026759 A150599 A150600 * A150601 A150602 A150603
Adjacent sequences: A005765 A005766 A005767 * A005769 A005770 A005771
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KEYWORD
| nonn
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AUTHOR
| Simon Plouffe (simon.plouffe(AT)gmail.com)
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EXTENSIONS
| Better description from Markus Voege (voege(AT)blagny.inria.fr), Nov 28 2003
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