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A139623 Table read by rows: T(n,k) is the number of directed multigraphs with loops and no vertex of degree 0, with n arcs and k vertices, which are transitive (the existence of a path between two points implies the existence of an arc between those two points). 4
1, 1, 1, 4, 3, 1, 1, 7, 12, 9, 3, 1, 1, 13 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Length of the n^th row: 2n.

T(n,1) = T(n,2n) = 1 and T(n,2n-1) = 3 if n>1.

Row sums: A139628.

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

Triangle begins

1, 1;

1, 4, 3, 1;

1, 7, 12, 9, 3, 1;

CROSSREFS

Cf. A136564, A139624, A139625.

Sequence in context: A157464 A046546 A189967 * A278072 A216482 A080758

Adjacent sequences:  A139620 A139621 A139622 * A139624 A139625 A139626

KEYWORD

nonn,tabf,more

AUTHOR

Benoit Jubin, May 01 2008

STATUS

approved

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Last modified May 16 15:55 EDT 2021. Contains 343949 sequences. (Running on oeis4.)