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A212693 Number of legal 7 X 6 Connect-Four positions after n plies. 4
1, 7, 49, 238, 1120, 4263, 16422, 54859, 184275, 558186, 1662623, 4568683, 12236101, 30929111, 75437595, 176541259, 394591391, 858218743, 1763883894, 3568259802, 6746155945, 12673345045, 22010823988, 38263228189, 60830813459, 97266114959, 140728569039 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Sum of all 43 terms is 4531985219092 as computed by Edelkamp and Kissmann (see link).

LINKS

John Tromp, Table of n, a(n) for n = 0..42 (copied from the P. Kissmann link)

S. Edelkamp and P. Kissmann, Symbolic Classification of General Two-Player Games

Brady Haran, Connect Four - Numberphile (video), 2013

P. Kissmann, Algorithm Engineering - Symbolische Suche

John Tromp, John's Connect Four Playground

EXAMPLE

a(3) = 7 * (1*7 + 6*(5/2 + 2)) = 238 because 3 discs played in different columns can be transposed in two ways.

CROSSREFS

Cf. A090224 (upper bound), A013582.

Sequence in context: A141783 A181479 A223842 * A223615 A188768 A188757

Adjacent sequences:  A212690 A212691 A212692 * A212694 A212695 A212696

KEYWORD

nonn,fini,full

AUTHOR

John Tromp, May 23 2012

STATUS

approved

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Last modified December 9 21:41 EST 2016. Contains 278987 sequences.