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A226252
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Number of ways of writing n as the sum of 7 triangular numbers.
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15
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1, 7, 21, 42, 77, 126, 175, 253, 357, 434, 567, 735, 833, 1057, 1302, 1400, 1708, 2037, 2191, 2597, 3003, 3151, 3619, 4242, 4389, 4935, 5691, 5740, 6594, 7434, 7371, 8400, 9303, 9506, 10626, 11592, 11585, 12761, 14427, 14203, 15519, 17241, 16808, 18788, 20559, 19950, 21882, 23898, 23786
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listen;
history;
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internal format)
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OFFSET
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0,2
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LINKS
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Seiichi Manyama, Table of n, a(n) for n = 0..10000
K. Ono, S. Robins and P. T. Wahl, On the representation of integers as sums of triangular numbers, Aequationes mathematicae, August 1995, Volume 50, Issue 1-2, pp 73-94.
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FORMULA
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G.f. is 7th power of g.f. for A010054.
a(0) = 1, a(n) = (7/n)*Sum_{k=1..n} A002129(k)*a(n-k) for n > 0. - Seiichi Manyama, May 06 2017
G.f.: exp(Sum_{k>=1} 7*(x^k/k)/(1 + x^k)). - Ilya Gutkovskiy, Jul 31 2017
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CROSSREFS
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Number of ways of writing n as a sum of k triangular numbers, for k=1,...: A010054, A008441, A008443, A008438, A008439, A008440, A226252, A007331, A226253, A226254, A226255, A014787, A014809.
Sequence in context: A205864 A162818 A024966 * A022602 A054569 A077354
Adjacent sequences: A226249 A226250 A226251 * A226253 A226254 A226255
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane, Jun 01 2013
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STATUS
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approved
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