OFFSET
0,3
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..160
Hsien-Kuei Hwang, Emma Yu Jin, Asymptotics and statistics on Fishburn matrices and their generalizations, arXiv:1911.06690 [math.CO], 2019.
FORMULA
a(n) ~ 12^(n+1) * n^(2*n+1) / (exp(2*n) * Pi^(2*n+1)). - Vaclav Kotesovec, Nov 04 2014
EXAMPLE
E.g.f.: A(x) = 1 + x + 4*x^2/2! + 42*x^3/3! + 804*x^4/4! + 24200*x^5/5! + ...
where
A(x) = 1 + x*(exp(x)-1)/(exp(x)-1) + x^2*(exp(x)-1)*(exp(2*x)-1)/(exp(x)-1)^2 + x^3*(exp(x)-1)*(exp(2*x)-1)*(exp(3*x)-1)/(exp(x)-1)^3 + ...
Equivalently,
A(x) = 1 + x + x^2*(exp(x)+1) + x^3*(exp(x)+1)*(exp(2*x)+exp(x)+1) + x^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*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