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A027786
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a(n) = 13*(n+1)*binomial(n+2,13)/2.
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1
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78, 1183, 9555, 54600, 247520, 946764, 3174444, 9573720, 26453700, 67897830, 163601438, 373173528, 811246800, 1690097500, 3389852700, 6571099080, 12351232530, 22574731725, 40219349625, 69995780400, 119218619520, 199052516520, 326270653800, 525704634000
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OFFSET
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11,1
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COMMENTS
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Number of 16-subsequences of [ 1, n ] with just 2 contiguous pairs.
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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*(6+x)*x^11/(1-x)^15.
Sum_{n>=11} 1/a(n) = 632203177/16008300 - 4*Pi^2.
Sum_{n>=11} (-1)^(n+1)/a(n) = 2*Pi^2 + 2277376*log(2)/1155 - 22194594643/16008300. (End)
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MATHEMATICA
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Table[13 (n + 1) Binomial[n + 2, 13]/2, {n, 11, 40}] (* Wesley Ivan Hurt, Mar 30 2017 *)
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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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