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).

1, 1, 1, 4, 3, 1, 1, 7, 12, 9, 3, 1, 1, 13

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 A358710 A216482

Adjacent sequences: A139620 A139621 A139622 * A139624 A139625 A139626

Keyword

nonn,tabf,more

Author

Benoit Jubin, May 01 2008

Status

approved