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A052332 Number of labeled digraphs where every node has indegree 0 or outdegree 0 and no isolated nodes. 8
1, 0, 2, 6, 50, 510, 7682, 161406, 4747010, 194342910, 11084390402, 881008805886, 97779099906050, 15178191426486270, 3302331237256396802, 1008694542117649154046, 433286992912494943469570 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Also labeled graphs with 2-colored nodes with no isolated nodes where black nodes are only connected to white nodes and vice versa.

LINKS

Table of n, a(n) for n=0..16.

FORMULA

a(n) = Sum_{k=0..n} (-1)^(n-k)*binomial(n, k)*A001831(k)

a(n) = Sum_{k=0..n} binomial(n, k)*(2^k-2)^(n-k). - Vladeta Jovovic, Apr 04 2003

CROSSREFS

Cf. A001831 (binomial transform), A002031, A047863.

Sequence in context: A103990 A079835 A177454 * A238596 A134047 A078464

Adjacent sequences:  A052329 A052330 A052331 * A052333 A052334 A052335

KEYWORD

nonn

AUTHOR

Christian G. Bower, Dec 15 1999

EXTENSIONS

Last 4 terms corrected by Vladeta Jovovic, Apr 04 2003

STATUS

approved

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Last modified November 17 05:27 EST 2019. Contains 329217 sequences. (Running on oeis4.)