OFFSET
0,2
COMMENTS
Self-convolution of A299437.
LINKS
Paul D. Hanna, Table of n, a(n) for n = 0..1000
EXAMPLE
G.f.: A(x) = 1 + 2*x + 5*x^2 + 10*x^3 + 24*x^4 + 44*x^5 + 109*x^6 + 198*x^7 + 423*x^8 + 766*x^9 + 1555*x^10 + 2730*x^11 + 6269*x^12 + 11090*x^13 + ...
such that
log(A(x)) = 2*x + 6*x^2/2 + 8*x^3/3 + 30*x^4/4 + 12*x^5/5 + 168*x^6/6 + 16*x^7/7 + 270*x^8/8 + 80*x^9/9 + 396*x^10/10 + 24*x^11/11 + 10920*x^12/12 + 28*x^13/13 + 720*x^14/14 + 768*x^15/15 + ... + A020696(n)*x^n/n + ...
PROG
(PARI) A020696(n) = {d = divisors(n); return (prod(i=1, #d, d[i]+1)); } \\ after Michel Marcus
{a(n) = my(A = exp( sum(m=1, n, A020696(m)*x^m/m ) +x*O(x^n) )); polcoeff(A, n)}
for(n=0, 40, print1(a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Feb 12 2018
STATUS
approved