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 A226252 Number of ways of writing n as the sum of 7 triangular numbers. 15
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS 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. FORMULA 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 CROSSREFS 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 KEYWORD nonn AUTHOR N. J. A. Sloane, Jun 01 2013 STATUS approved

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Last modified December 11 07:44 EST 2019. Contains 329914 sequences. (Running on oeis4.)