A003026 Number of n-node labeled acyclic digraphs with 2 out-points. (Formerly M4666)

1, 9, 198, 10710, 1384335, 416990763, 286992935964, 444374705175516, 1528973599758889005, 11573608032229769067465, 191141381932394665770442818, 6839625961762363728765713227698

Offset

2,2

References

R. W. Robinson, Counting labeled acyclic digraphs, pp. 239-273 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Andrew Howroyd, Table of n, a(n) for n = 2..50

Prog

(PARI) \\ requires A058876.
my(T=A058876(20)); vector(#T-1, n, T[n+1][2]) \\ Andrew Howroyd, Dec 27 2021

Crossrefs

A diagonal of A058876.

Cf. A003025.

Sequence in context: A019566 A338226 A157563 * A157594 A232276 A196910

Adjacent sequences: A003023 A003024 A003025 * A003027 A003028 A003029

Keyword

nonn

Author

N. J. A. Sloane

Extensions

More terms from Vladeta Jovovic, Apr 10 2001

Status

approved