A187508 - OEIS

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A187508

Number of 3-step S, E, and NW-moving king's tours on an n X n board summed over all starting positions

0, 6, 31, 74, 135, 214, 311, 426, 559, 710, 879, 1066, 1271, 1494, 1735, 1994, 2271, 2566, 2879, 3210, 3559, 3926, 4311, 4714, 5135, 5574, 6031, 6506, 6999, 7510, 8039, 8586, 9151, 9734, 10335, 10954, 11591, 12246, 12919, 13610, 14319, 15046, 15791

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Row 3 of A187507

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..50

FORMULA

Empirical: a(n) = 9*n^2 - 20*n + 10 for n>1.

Empirical G.f.: x^2*(6+13*x-x^2)/(1-x)^3. [Colin Barker, Jan 22 2012]

EXAMPLE

Some solutions for 4X4