OFFSET
0,2
EXAMPLE
A(x) = 1 + 3*x + 12*x^2 + 39*x^3 + 138*x^4 + 426*x^5 + ... =
1/[(1-3*x)*(1-9*x^2)^(1/3)*(1-27*x^3)^(1/9)*(1-81*x^4)^(1/27)*...].
MATHEMATICA
nmax=27; CoefficientList[Series[Product[1/(1 - 3^n*x^n)^(3/3^n), {n, nmax}], {x, 0, nmax}], x] (* Stefano Spezia, Jun 21 2024 *)
PROG
(PARI) a(n)=polcoeff(prod(k=1, n, 1/(1-3^k*x^k+x*O(x^n))^(3/3^k)), n)
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jul 14 2005
EXTENSIONS
a(25)-a(27) from Stefano Spezia, Jun 21 2024
STATUS
approved