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A187292 Number of 7-step one or two space at a time rook's tours on an n X n board summed over all starting positions. 1
0, 0, 2304, 47648, 228512, 616752, 1241936, 2102944, 3192912, 4505424, 6037932, 7789392, 9759616, 11948560, 14356224, 16982608, 19827712, 22891536, 26174080, 29675344, 33395328, 37334032, 41491456, 45867600, 50462464, 55276048, 60308352 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Row 7 of A187286.

LINKS

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

FORMULA

Empirical: a(n) = 109360*n^2 - 763776*n + 1206864 for n>11.

Conjectures from Colin Barker, Apr 23 2018: (Start)

G.f.: 4*x^3*(576 + 10184*x + 23120*x^2 + 17964*x^3 + 7392*x^4 - 280*x^5 - 1716*x^6 - 1604*x^7 - 637*x^8 - 261*x^9 - 47*x^10 - 11*x^11) / (1 - x)^3.

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>14.

(End)

EXAMPLE

Some solutions for 4 X 4:

..0..0..0..0....0..0..0..0....0..1..0..0....2..3..0..0....6..5..7..0

..0..5..6..4....0..0..7..0....3..2..7..0....1..5..7..6....0..0..0..0

..1..2..0..3....4..1..5..0....5..0..6..0....0..4..0..0....0..4..0..3

..0..0..7..0....3..2..6..0....4..0..0..0....0..0..0..0....0..1..0..2

CROSSREFS

Cf. A187286.

Sequence in context: A204102 A177759 A218431 * A235423 A235419 A229698

Adjacent sequences:  A187289 A187290 A187291 * A187293 A187294 A187295

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 08 2011

STATUS

approved

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Last modified January 19 04:09 EST 2020. Contains 331031 sequences. (Running on oeis4.)