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A187509 Number of 4-step S, E, and NW-moving king's tours on an n X n board summed over all starting positions 1
0, 2, 36, 115, 236, 399, 604, 851, 1140, 1471, 1844, 2259, 2716, 3215, 3756, 4339, 4964, 5631, 6340, 7091, 7884, 8719, 9596, 10515, 11476, 12479, 13524, 14611, 15740, 16911, 18124, 19379, 20676, 22015, 23396, 24819, 26284, 27791, 29340, 30931, 32564, 34239 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 4 of A187507

LINKS

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

FORMULA

Empirical: a(n) = 21*n^2 - 68*n + 51 for n>2.

Empirical G.f.: x^2*(2+30*x+13*x^2-3*x^3)/(1-x)^3. [Colin Barker, Jan 22 2012]

EXAMPLE

Some solutions for 4X4

..0..0..0..0....0..0..0..0....0..4..2..0....0..4..0..0....0..0..0..0

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

..0..0..4..0....0..2..3..0....0..0..0..0....0..0..1..0....0..0..3..4

..0..0..0..0....0..0..4..0....0..0..0..0....0..0..0..0....0..0..0..0

CROSSREFS

Sequence in context: A258356 A145450 A196558 * A134785 A143745 A199944

Adjacent sequences:  A187506 A187507 A187508 * A187510 A187511 A187512

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 10 2011

STATUS

approved

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Last modified December 6 22:42 EST 2021. Contains 349567 sequences. (Running on oeis4.)