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A187174 Number of 4-step left-handed knight's tours (moves only out two, left one) on an n X n board summed over all starting positions. 1
0, 0, 0, 8, 48, 176, 384, 664, 1016, 1440, 1936, 2504, 3144, 3856, 4640, 5496, 6424, 7424, 8496, 9640, 10856, 12144, 13504, 14936, 16440, 18016, 19664, 21384, 23176, 25040, 26976, 28984, 31064, 33216, 35440, 37736, 40104, 42544, 45056, 47640, 50296 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Row 4 of A187172.

LINKS

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

FORMULA

Empirical: a(n) = 36*n^2 - 260*n + 440 for n>5.

G.f.: 8*x^4*(1 + 3*x + 7*x^2 - x^3 - x^4) / (1 - x)^3 (conjectured). - Colin Barker, Apr 22 2018

EXAMPLE

Some solutions for 4 X 4:

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

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

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

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

CROSSREFS

Cf. A187172.

Sequence in context: A073912 A212571 A247727 * A128796 A093199 A263507

Adjacent sequences:  A187171 A187172 A187173 * A187175 A187176 A187177

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 06 2011

STATUS

approved

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Last modified January 27 04:57 EST 2020. Contains 331291 sequences. (Running on oeis4.)