OFFSET
0,2
FORMULA
a(n) = 9^n * Sum_{k>=0} (1/2)^(k+1) * binomial(k/3,n).
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(1/(2-(1+9*x)^(1/3)))
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Seiichi Manyama, Aug 04 2024
STATUS
approved