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A049512 Number of quasi-initially connected digraphs on n unlabeled nodes. 4
1, 2, 13, 197, 9312, 1528634, 880277970 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

From Sean A. Irvine, Aug 01 2021: (Start)

A quasi-initially connected digraph is a digraph containing at least one vertex v such that every vertex u in the graph can either be reached from v or v can be reached from u (while obeying the directions on the edges).

There is no known formula. (End)

LINKS

Table of n, a(n) for n=1..7.

Sean A. Irvine, Java program (github)

V. Jovovic and G. Kilibarda, Enumeration of labeled quasi-initially connected digraphs, Discrete Math., 224 (2000), 151-163.

CROSSREFS

Cf. A049414, A003085, A035512, A003088, A051421.

Sequence in context: A323209 A239994 A242007 * A003507 A338979 A307066

Adjacent sequences:  A049509 A049510 A049511 * A049513 A049514 A049515

KEYWORD

hard,more,nonn

AUTHOR

Vladeta Jovovic, Goran Kilibarda

EXTENSIONS

a(6)-a(7) from Sean A. Irvine, Aug 01 2021

STATUS

approved

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Last modified October 6 09:29 EDT 2022. Contains 357263 sequences. (Running on oeis4.)