OFFSET
0,3
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..160
EXAMPLE
E.g.f.: A(x) = 1 + x + 2*x^2/2! + 9*x^3/3! + 66*x^4/4! + 680*x^5/5! +...
where
A(x) = 1 + x*(exp(x)-1)/(exp(x)-1) + x^2/2!*(exp(x)-1)*(exp(2*x)-1)/(exp(x)-1)^2 + x^3/3!*(exp(x)-1)*(exp(2*x)-1)*(exp(3*x)-1)/(exp(x)-1)^3 +...
Equivalently,
A(x) = 1 + x + x^2/2!*(exp(x)+1) + x^3/3!*(exp(x)+1)*(exp(2*x)+exp(x)+1) + x^4/4!*(exp(x)+1)*(exp(2*x)+exp(x)+1)*(exp(3*x)+exp(2*x)+exp(x)+1) +...
PROG
(PARI) {a(n)=n!*polcoeff(1+sum(m=1, n, x^m/m!*prod(k=1, m, (exp(k*x+x*O(x^n))-1)/(exp(x+x*O(x^n))-1))), n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Sep 28 2011
STATUS
approved