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A027773
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a(n) = (n+1)*binomial(n+1,13).
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2
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13, 196, 1575, 8960, 40460, 154224, 515508, 1550400, 4273290, 10943240, 26313518, 59907456, 130007500, 270415600, 541574100, 1048380480, 1968053535, 3592795500, 6393845325, 11115955200, 18914492520, 31551447840, 51671823000, 83188425600, 131811290100
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OFFSET
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12,1
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COMMENTS
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Number of 15-subsequences of [ 1, n ] with just 1 contiguous pair.
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (15,-105,455,-1365,3003,-5005,6435,-6435,5005,-3003,1365,-455,105,-15,1).
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FORMULA
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G.f.: (13+x)*x^12/(1-x)^15.
Sum_{n>=12} 1/a(n) = 13*Pi^2/6 - 8183956651/384199200.
Sum_{n>=12} (-1)^n/a(n) = 13*Pi^2/12 + 34451456*log(2)/3465 - 2651886676309/384199200. (End)
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MATHEMATICA
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(#+1)Binomial[#+1, 13]&/@Range[12, 40] (* Harvey P. Dale, Mar 18 2011 *)
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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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