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 A090224 Number of possible positions for n discs on a standard 7 X 6 board of Connect-Four. 4
 1, 7, 56, 252, 1260, 4620, 18480, 59815, 206780, 605934, 1869840, 5038572, 14164920, 35459424, 91871208, 214864650, 516936420, 1134183050, 2546423880, 5252058812, 11031780760, 21406686756, 42121344720, 76871042612, 141627466344, 242619996500, 417750499600 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..42 (copied from the Victor Allis link) John Tromp, John's Connect Four Playground, viewed Jan 23 2014. Eric Weisstein's World of Mathematics, Connect-Four Wikipedia, Connect Four EXAMPLE a(2) = 2 * binomial(8,2) since there are binomial(8,2) ways to distribute 2 discs over 7 columns and 2 ways to color them black and white. - John Tromp, May 24 2012 CROSSREFS Cf. A212693 (legal positions after n plies). Sequence in context: A044526 A153797 A244727 * A237647 A047664 A055345 Adjacent sequences:  A090221 A090222 A090223 * A090225 A090226 A090227 KEYWORD nonn,fini,full,nice AUTHOR Eric W. Weisstein, Nov 24 2003 STATUS approved

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Last modified April 22 12:36 EDT 2021. Contains 343177 sequences. (Running on oeis4.)