OFFSET
0,4
REFERENCES
R. W. Robinson, Counting labeled acyclic digraphs, p. 264 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..50
MATHEMATICA
m = 20; b[0] = b[1] = 1;
b[n_] := b[n] = Sum[-(-1)^k Binomial[n, k] 2^(k (n-k)) b[n-k], {k, 1, n}];
B[x_] = Sum[b[n] x^n/n!, {n, 0, m}];
CoefficientList[1 - 1/B[x] + O[x]^(m+1), x] Range[0, m]! (* Jean-François Alcover, Jan 24 2020 *)
PROG
(PARI) \\ here G(n) gives A003024 as e.g.f.
G(n)={my(v=vector(n+1)); v[1]=1; for(n=1, n, v[n+1]=sum(k=1, n, -(-1)^k*2^(k*(n-k))*v[n-k+1]/k!))/n!; Ser(v)}
{ concat([0], Vec(serlaplace(1-1/G(15)))) } \\ Andrew Howroyd, Sep 10 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, Apr 15 2003
STATUS
approved