

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
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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 12, pp 7394.


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(nk) 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



