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A121137 Number of labeled directed multigraphs (without loops) with n arcs and no vertex of degree 0. 1
1, 2, 27, 572, 16787, 631362, 28980861, 1570956872, 98212870233, 6956704585554, 550626446263423, 48163137319172436, 4613554511554200251, 480324019903607680066, 54004504167811544647161, 6521368218660772789452944 (list; graph; refs; listen; history; text; internal format)
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

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Last modified January 23 16:29 EST 2022. Contains 350514 sequences. (Running on oeis4.)