OFFSET
0,2
COMMENTS
Self-convolution of A062051.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..10000
FORMULA
G.f.: Product_{k>=0} 1/(1 - x^(3^k))^2.
MAPLE
b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<0, 0,
b(n, i-1)+(p-> `if`(p>n, 0, b(n-p, i)))(3^i)))
end:
a:= n-> add(b(j, ilog[3](j))*b(n-j, ilog[3](n-j)), j=0..n):
seq(a(n), n=0..52); # Alois P. Heinz, Aug 12 2019
MATHEMATICA
nmax = 52; A[_] = 1; Do[A[x_] = A[x^3]/(1 - x)^2 + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
nmax = 52; CoefficientList[Series[Product[1/(1 - x^(3^k))^2, {k, 0, Floor[Log[3, nmax]] + 1}], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Aug 12 2019
STATUS
approved