OFFSET
0,27
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
FORMULA
A(x) = Sum_{k>=0} a(k) * x^k = Product_{k>=0} (1+x^(4*k+1))^a(k).
A(x) * A(i*x) * A(-x) * A(i^3*x) = A(-x^4), where i=sqrt(-1).
a(0) = 1; a(n) = (1/n) * Sum_{k=1..n} ( Sum_{d|k and d==1 mod 4} (-1)^(k/d+1) * d * a(floor(d/4)) ) * a(n-k).
PROG
(PARI) seq(n) = my(A=1); for(i=1, n, A=exp(sum(k=1, i, (-1)^(k+1)*subst(A, x, x^(4*k))*x^k/k)+x*O(x^n))); Vec(A);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, May 28 2023
STATUS
approved