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A007786
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Number of nonintersecting rook paths joining opposite corners of 4 X n board.
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8
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1, 8, 38, 184, 976, 5382, 29739, 163496, 896476, 4913258, 26932712, 147657866, 809563548, 4438573234, 24335048679, 133419610132, 731487691902, 4010463268476, 21987818897998, 120550710615560, 660932932108467
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OFFSET
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1,2
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REFERENCES
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Netnews group rec.puzzles, Frequently Asked Questions (FAQ) file. (Science Section).
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LINKS
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D. G. Radcliffe, N. J. A. Sloane, C. Cole, J. Gillogly, & D. Dodson, Emails, 1994
Index entries for linear recurrences with constant coefficients, signature (12,-54,124,-133,-16,175,-94,-69,40,12,-4,-1).
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FORMULA
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a(n) = 12*a(n - 1) - 54*a(n - 2) + 124*a(n - 3) - 133*a(n - 4) - 16*a(n - 5) + 175*a(n - 6) - 94*a(n - 7) - 69*a(n - 8) + 40*a(n - 9) + 12*a(n - 10) - 4*a(n - 11) - a(n - 12). - Vladeta Jovovic, Mar 20 2000
G.f.: x*(x^10-15*x^8+6*x^7+50*x^6-26*x^5-39*x^4+36*x^3-4*x^2-4*x+1) / ((x^6+2*x^5-9*x^4-5*x^3+15*x^2-8*x+1)*(x^6+2*x^5-7*x^4-3*x^3+7*x^2-4*x+1)). [Colin Barker, Nov 24 2012]
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MATHEMATICA
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LinearRecurrence[{12, -54, 124, -133, -16, 175, -94, -69, 40, 12, -4, -1}, {1, 8, 38, 184, 976, 5382, 29739, 163496, 896476, 4913258, 26932712, 147657866}, 30] (* Harvey P. Dale, Jun 27 2012 *)
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CROSSREFS
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KEYWORD
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nonn,easy,nice,walk
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AUTHOR
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Heiner Marxen
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EXTENSIONS
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STATUS
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approved
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