OFFSET
0,2
FORMULA
A(x) = B(x)/(1 + 3*x) where B(x) is the g.f. of A363581.
A(x) = Sum_{k>=0} a(k) * x^k = 1/(1+3*x) * 1/Product_{k>=0} (1-x^(k+1))^a(k).
a(0) = 1; a(n) = (1/n) * Sum_{k=1..n} ( (-3)^k + Sum_{d|k} d * a(d-1) ) * a(n-k).
PROG
(PARI) seq(n) = my(A=1); for(i=1, n, A=exp(sum(k=1, i, ((-3)^k+subst(A, x, x^k))*x^k/k)+x*O(x^n))); Vec(A);
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Jun 10 2023
STATUS
approved