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A213832
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Principal diagonal of the convolution array A213831.
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3
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1, 19, 78, 202, 415, 741, 1204, 1828, 2637, 3655, 4906, 6414, 8203, 10297, 12720, 15496, 18649, 22203, 26182, 30610, 35511, 40909, 46828, 53292, 60325, 67951, 76194, 85078, 94627, 104865, 115816, 127504
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OFFSET
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1,2
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LINKS
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FORMULA
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G.f.: x*(1 + 15*x + 8*x^2)/(1-x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4).
a(n) = (n - 7*n^2 + 8*n^3)/2.
a(n) = Sum_{i = 0..n-1} (n + i)*(n + 3*i). - Bruno Berselli, Feb 14 2018
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MATHEMATICA
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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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