OFFSET
0,3
LINKS
E. de Panafieu and S. Dovgal, Symbolic method and directed graph enumeration, arXiv:1903.09454 [math.CO], 2019.
R. W. Robinson, Counting digraphs with restrictions on the strong components, Combinatorics and Graph Theory '95 (T.-H. Ku, ed.), World Scientific, Singapore (1995), 343-354.
Wikipedia, Strongly connected component
MATHEMATICA
nn = 15; B[n_] := n! 2^Binomial[n, 2]; a[x_] := Exp[x] - 1; Table[B[n], {n, 0, nn}] CoefficientList[Series[1/Normal[Series[Exp[-(Exp[x] - 1)], {x, 0, nn}]] /.
Table[x^i -> z^i/2^Binomial[i, 2], {i, 0, nn}], {z, 0, nn}], z]
CROSSREFS
KEYWORD
nonn
AUTHOR
Geoffrey Critzer, Mar 15 2023
STATUS
approved