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 A005770 Number of convex polygons of length 2n on square lattice whose leftmost bottom vertex and rightmost top vertex have the same x-coordinate. (Formerly M4638) 4
 1, 9, 55, 286, 1362, 6143, 26729, 113471, 473471, 1951612, 7974660, 32384127, 130926391, 527657073, 2121795391, 8518575466, 34162154550, 136893468863, 548253828965, 2194897467395, 8784784672511, 35153438973304, 140653028240520, 562719731644671 (list; graph; refs; listen; history; text; internal format)
 OFFSET 5,2 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). LINKS Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992. Simon Plouffe, 1031 Generating Functions and Conjectures, Université du Québec à Montréal, 1992. FORMULA a(n) = A005436(n) - A005768(n) - A005769(n). G.f.: x^5*(1-3*x+2*x^2+x^3)/((1-2*x^(1/2))*(1+2*x^(1/2))*(1-2*x)*(1+x^(1/2)-x)^2*(1-x^(1/2)-x)^2). - Markus Voege (voege(AT)blagny.inria.fr), Nov 28 2003 MAPLE A005770:=(1-3*z+2*z**2+z**3)/(4*z-1)/(2*z-1)/(z**2-3*z+1)**2; # conjectured by Simon Plouffe in his 1992 dissertation CROSSREFS Sequence in context: A141530 A263478 A016269 * A030053 A072844 A026857 Adjacent sequences:  A005767 A005768 A005769 * A005771 A005772 A005773 KEYWORD nonn,easy AUTHOR EXTENSIONS Better description from Markus Voege (voege(AT)blagny.inria.fr), Nov 28 2003 More terms from Sean A. Irvine, Aug 26 2016 STATUS approved

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Last modified December 9 16:41 EST 2018. Contains 318023 sequences. (Running on oeis4.)