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A264853
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a(n) = n*(n + 1)*(5*n^2 + 5*n - 4)/12.
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2
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0, 1, 13, 56, 160, 365, 721, 1288, 2136, 3345, 5005, 7216, 10088, 13741, 18305, 23920, 30736, 38913, 48621, 60040, 73360, 88781, 106513, 126776, 149800, 175825, 205101, 237888, 274456, 315085, 360065, 409696, 464288, 524161, 589645, 661080, 738816, 823213, 914641
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OFFSET
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0,3
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COMMENTS
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Partial sums of centered 10-gonal (or decagonal) pyramidal numbers.
Subsequence of A204221. In fact, a(n) is of the form (k^2-1)/15 for k = 5*n*(n+1)/2-1. - Bruno Berselli, Nov 27 2015
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LINKS
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Table of n, a(n) for n=0..38.
OEIS Wiki, Figurate numbers
Eric Weisstein's World of Mathematics, Pyramidal Number
Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1).
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FORMULA
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G.f.: x*(1 + 8*x + x^2)/(1 - x)^5.
a(n) = Sum_{k = 0..n} A004466(k).
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5). - Vincenzo Librandi, Nov 27 2015
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MATHEMATICA
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Table[n (n + 1) (5 n^2 + 5 n - 4)/12, {n, 0, 50}]
LinearRecurrence[{5, -10, 10, -5, 1}, {0, 1, 13, 56, 160}, 40] (* Harvey P. Dale, Aug 14 2017 *)
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PROG
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(MAGMA) [n*(n+1)*(5*n^2+5*n-4)/12: n in [0..50]]; // Vincenzo Librandi, Nov 27 2015
(PARI) a(n)=n*(n+1)*(5*n^2+5*n-4)/12 \\ Charles R Greathouse IV, Jul 26 2016
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CROSSREFS
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Cf. A004466, A204221.
Cf. similar sequences listed in A264854.
Sequence in context: A290396 A061161 A212053 * A210290 A007202 A222161
Adjacent sequences: A264850 A264851 A264852 * A264854 A264855 A264856
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KEYWORD
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nonn,easy
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AUTHOR
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Ilya Gutkovskiy, Nov 26 2015
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STATUS
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approved
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