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A187177 Number of 7-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, 0, 0, 16, 368, 1600, 4284, 8760, 15104, 23144, 32764, 43944, 56684, 70984, 86844, 104264, 123244, 143784, 165884, 189544, 214764, 241544, 269884, 299784, 331244, 364264, 398844, 434984, 472684, 511944, 552764, 595144, 639084, 684584 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

Row 7 of A187172.

LINKS

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

FORMULA

Empirical: a(n) = 780*n^2 - 9880*n + 29384 for n>11.

G.f.: 4*x^6*(4 + 80*x + 136*x^2 + 143*x^3 + 85*x^4 + 19*x^5 - 43*x^6 - 29*x^7 - 5*x^8) / (1 - x)^3 (conjectured). - Colin Barker, Apr 22 2018

EXAMPLE

Some solutions for 6 X 6:

..0..0..3..0..0..0....0..1..0..0..0..0....0..0..0..6..0..0....0..0..0..4..0..0

..4..0..0..0..0..1....0..0..0..0..7..0....0..7..0..0..0..0....0..5..0..0..0..0

..0..0..0..2..0..0....0..0..2..0..0..0....0..0..0..0..5..0....0..0..0..0..3..0

..0..5..0..0..0..0....3..0..0..0..0..6....0..0..2..0..0..0....0..0..6..0..0..0

..0..0..0..0..7..0....0..0..0..5..0..0....1..0..0..0..0..4....7..0..0..0..0..2

..0..0..6..0..0..0....0..4..0..0..0..0....0..0..0..3..0..0....0..0..0..1..0..0

CROSSREFS

Cf. A187172.

Sequence in context: A276097 A265476 A008427 * A053105 A220576 A264186

Adjacent sequences:  A187174 A187175 A187176 * A187178 A187179 A187180

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 06 2011

STATUS

approved

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Last modified February 17 21:35 EST 2020. Contains 332006 sequences. (Running on oeis4.)