OFFSET
0,8
COMMENTS
Number of partitions of n into nonzero hexagonal pyramidal numbers (A002412).
LINKS
M. Bernstein and N. J. A. Sloane, Some canonical sequences of integers, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to arXiv version]
M. Bernstein and N. J. A. Sloane, Some canonical sequences of integers, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to Lin. Alg. Applic. version together with omitted figures]
Eric Weisstein's World of Mathematics, Hexagonal Pyramidal Number
FORMULA
G.f.: Product_{k>=1} 1/(1 - x^(k*(k+1)*(4*k-1)/6)).
EXAMPLE
a(8) = 2 because we have [7, 1] and [1, 1, 1, 1, 1, 1, 1, 1].
MATHEMATICA
nmax=90; CoefficientList[Series[Product[1/(1 - x^(k (k + 1) (4 k - 1)/6)), {k, 1, nmax}], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Dec 08 2016
STATUS
approved