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A242983
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n/2 * (n^3 - 2*n^2 - 2*n + 5).
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0
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0, 1, 1, 12, 58, 175, 411, 826, 1492, 2493, 3925, 5896, 8526, 11947, 16303, 21750, 28456, 36601, 46377, 57988, 71650, 87591, 106051, 127282, 151548, 179125, 210301, 245376, 284662, 328483, 377175, 431086, 490576, 556017
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OFFSET
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0,4
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COMMENTS
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For n>1, number of ways to place two dominoes horizontally on an n X n chessboard.
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LINKS
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FORMULA
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G.f.: x*(-2*x^3 + 17*x^2 - 4*x + 1) / (1-x)^5.
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MATHEMATICA
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Table[n/2 (n^3-2n^2-2n+5), {n, 0, 40}] (* or *) LinearRecurrence[{5, -10, 10, -5, 1}, {0, 1, 1, 12, 58}, 40] (* Harvey P. Dale, Jul 19 2018 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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