

A212693


Number of legal 7 X 6 ConnectFour 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 TwoPlayer 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



