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A011875
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Floor( n*(n-1)/22 ).
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1
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0, 0, 0, 0, 0, 0, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 34, 36, 39, 42, 45, 48, 51, 54, 57, 60, 63, 67, 70, 74, 78, 82, 86, 90, 94, 98, 102, 106, 111, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 166, 171, 177, 183, 189, 195, 201, 207
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OFFSET
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0,9
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (2, -1, 0, 0, 0, 0, 0, 0, 0, 0, 1, -2, 1).
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FORMULA
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a(n) = +2*a(n-1) -a(n-2) +a(n-11) -2*a(n-12) +a(n-13). G.f.: x^6*(x^2-x+1) / ((1-x)^3*(1+x^10+x^9+x^8+x^7+x^6+x^5+x^4+x^3+x^2+x) ). [R. J. Mathar, Apr 15 2010]
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MATHEMATICA
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Table[Floor[(n(n-1))/22], {n, 0, 70}] (* or *) LinearRecurrence[{2, -1, 0, 0, 0, 0, 0, 0, 0, 0, 1, -2, 1}, {0, 0, 0, 0, 0, 0, 1, 1, 2, 3, 4, 5, 6}, 70]
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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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