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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 1
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

..0..0..0..0....0..0..0..0....1..0..0..0....0..2..0..0....3..1..0..0

..0..2..3..0....3..0..0..0....2..3..0..0....0..3..1..0....0..2..0..0

..0..0..1..0....0..2..0..0....0..0..0..0....0..0..0..0....0..0..0..0

..0..0..0..0....0..0..1..0....0..0..0..0....0..0..0..0....0..0..0..0

CROSSREFS

Sequence in context: A025524 A042841 A215730 * A087725 A273790 A096959

Adjacent sequences:  A187505 A187506 A187507 * A187509 A187510 A187511

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 10 2011

STATUS

approved

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Last modified February 24 01:16 EST 2020. Contains 332195 sequences. (Running on oeis4.)