OFFSET
0,4
COMMENTS
These are the directed graphs whose strong components exclude a single vertex. - Andrew Howroyd, Jan 15 2022
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..50
Valery Liskovets, Labeled digraphs in which every node belongs to a directed cycle [Broken link]
PROG
(PARI)
G(p)={my(n=serprec(p, x)); serconvol(p, sum(k=0, n-1, x^k/2^(k*(k-1)/2), O(x^n)))}
U(p)={my(n=serprec(p, x)); serconvol(p, sum(k=0, n-1, x^k*2^(k*(k-1)/2), O(x^n)))}
DigraphEgf(n)={sum(k=0, n, 2^(k*(k-1))*x^k/k!, O(x*x^n) )}
seq(n)={Vec(serlaplace(U(1/G(exp(x+log(U(1/G(DigraphEgf(n)))))))))} \\ Andrew Howroyd, Jan 15 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Valery A. Liskovets and Vladeta Jovovic, Sep 04 2003
EXTENSIONS
a(0)=1 prepended and terms a(12) and beyond from Andrew Howroyd, Jan 15 2022
STATUS
approved