A121137 Number of labeled directed multigraphs (without loops) with n arcs and no vertex of degree 0.

1, 2, 27, 572, 16787, 631362, 28980861, 1570956872, 98212870233, 6956704585554, 550626446263423, 48163137319172436, 4613554511554200251, 480324019903607680066, 54004504167811544647161, 6521368218660772789452944

Offset

0,2

Links

Nathaniel Johnston, Table of n, a(n) for n = 0..50

Maple

seq(sum(binomial(m*(m-1)+n-1, n)/2^(m+1), m=0..infinity), n=0..10);

Crossrefs

Cf. A052170 (unlabeled analog), A104209, A052171.

Sequence in context: A240638 A245050 A242009 * A203429 A153850 A138458

Adjacent sequences: A121134 A121135 A121136 * A121138 A121139 A121140

Keyword

easy,nonn

Author

Vladeta Jovovic, Sep 06 2006

Status

approved