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0, 0, 2, 12, 39, 95, 195, 357, 602, 954, 1440, 2090, 2937, 4017, 5369, 7035, 9060, 11492, 14382, 17784, 21755, 26355, 31647, 37697, 44574, 52350, 61100, 70902, 81837, 93989, 107445, 122295, 138632, 156552, 176154, 197540, 220815, 246087
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) = 3*C(n+2,4) - C(n,2). - Zerinvary Lajos, May 02 2007, corrected Jun 12 2018
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) = n*(n-1)*(n^2+3*n-2)/8. [R. J. Mathar, Oct 30 2009]
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EXAMPLE
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a(3) = t(t(3))-3^2 = t(6)-9 = 21-9 = 12.
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MAPLE
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seq(3*binomial(n+2, 4)-binomial(n, 2), n=0..35); # Zerinvary Lajos, May 02 2007
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MATHEMATICA
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Table[n (n - 1) (n^2 + 3 n - 2)/8, {n, 0, 40}] (* Bruno Berselli, Aug 27 2014 *)
LinearRecurrence[{5, -10, 10, -5, 1}, {0, 0, 2, 12, 39}, 60] (* Harvey P. Dale, Apr 04 2023 *)
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PROG
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(PARI) t(i)=i*(i+1)/2
vector(40, i, t(t(i))-i^2)
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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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