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A317576
Irregular triangle read by rows: T(n,k) is the number of n X n tic-tac-toe positions (up to rotation and reflection) with k tokens (i.e., after k plays) which end a game (n > 0, 0 <= k <= n^2).
0
0, 1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 21, 21, 58, 23, 15, 0, 0, 0, 0, 0, 0, 0, 280, 642, 4942, 6770, 20286, 16042, 20998, 7970, 3774, 1059, 0, 0, 0, 0, 0, 0, 0, 0, 0
OFFSET
1,6
COMMENTS
If k < n^2, T(n,k) is the number of positions where X (odd k) or O (even k) has won after k plays. T(n,n^2) = A317575(n,n^2) counts draws as well.
The number of draw positions is T(n,n^2) - A317573(n,n^2) for odd n and T(n,n^2) - A317574(n,n^2) for even n.
FORMULA
For 0 <= k < 2n-1, T(n,k) = 0; T(n,2n-1) > 0.
EXAMPLE
Triangle begins:
n\k | 0 1 2 3 4 5 6 7 8 9
----+---------------------------------------
1 | 0 1
2 | 0 0 0 2 0
3 | 0 0 0 0 0 21 21 58 23 15
CROSSREFS
Cf. A317573-A317575, A048245 (3rd row).
Sequence in context: A053201 A028605 A319532 * A070205 A138363 A080225
KEYWORD
nonn,tabf,more
AUTHOR
Álvar Ibeas, Jul 31 2018
STATUS
approved