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 A005701 Number of exterior points formed by extending diagonals of n-gon in general position. (Formerly M2968) 5
 3, 14, 40, 90, 175, 308, 504, 780, 1155, 1650, 2288, 3094, 4095, 5320, 6800, 8568, 10659, 13110, 15960, 19250, 23023, 27324, 32200, 37700, 43875, 50778, 58464, 66990, 76415, 86800, 98208, 110704, 124355 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS See Gouyou-Beauchamps for an interpretation in terms of closed paths in the first quadrant of the square grid. REFERENCES L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 74, Problem 8. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 D. Gouyou-Beauchamps, Chemins sous-diagonaux et tableaux de Young, pp. 112-125 of "Combinatoire Enumerative (Montreal 1985)", Lect. Notes Math. 1234, Springer, 1986. D. Gouyou-Beauchamps, Chemins sous-diagonaux et tableaux de Young, pp. 112-125 of "Combinatoire Enumerative (Montreal 1985)", Lect. Notes Math. 1234, Springer, 1986. (Annotated scanned copy) FORMULA a(n) = (n+1)*(n+2)*(n+3)*(n+6)/12. G.f.: (x-3)/(x-1)^5 [Maksym Voznyy (voznyy(AT)mail.ru), Aug 10 2009] MATHEMATICA CoefficientList[Series[(x - 3) / (x - 1)^5, {x, 0, 50}], x] (* Vincenzo Librandi, Jun 09 2013 *) PROG (MAGMA) [(n+1)*(n+2)*(n+3)*(n+6)/12: n in [0..50]]; // Vincenzo Librandi, Jun 09 2013 (PARI) a(n) = (n+1)*(n+2)*(n+3)*(n+6)/12; \\ Michel Marcus, Dec 16 2017 CROSSREFS A diagonal of the triangle in A179898. Sequence in context: A102590 A174517 A034130 * A050297 A117662 A196236 Adjacent sequences:  A005698 A005699 A005700 * A005702 A005703 A005704 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified October 16 18:08 EDT 2018. Contains 316271 sequences. (Running on oeis4.)