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A008813
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Expansion of (1+x^6)/(1-x)^2/(1-x^6).
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1
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1, 2, 3, 4, 5, 6, 9, 12, 15, 18, 21, 24, 29, 34, 39, 44, 49, 54, 61, 68, 75, 82, 89, 96, 105, 114, 123, 132, 141, 150, 161, 172, 183, 194, 205, 216, 229, 242, 255, 268, 281, 294, 309, 324, 339, 354, 369, 384, 401, 418
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OFFSET
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0,2
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COMMENTS
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Number of 0..n arrays of 7 elements with zero second differences. [From R. H. Hardin, Nov 16 2011]
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LINKS
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Table of n, a(n) for n=0..49.
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FORMULA
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a(n) = 2*a(n-1) -a(n-2) +a(n-6) -2*a(n-7) +a(n-8). [From R. H. Hardin, Nov 16 2011]
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MATHEMATICA
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CoefficientList[Series[(1+x^6)/(1-x)^2/(1-x^6), {x, 0, 50}], x] (* or *) LinearRecurrence[{2, -1, 0, 0, 0, 1, -2, 1}, {1, 2, 3, 4, 5, 6, 9, 12}, 50] (* Harvey P. Dale, Oct 13 2012 *)
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PROG
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(PARI) Vec((1+x^6)/(1-x)+O(x^99)) \\ Charles R Greathouse IV, Sep 26 2012
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CROSSREFS
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Sequence in context: A091179 A036027 A036032 * A133463 A187550 A057492
Adjacent sequences: A008810 A008811 A008812 * A008814 A008815 A008816
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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