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 A139625 Table read by rows: T(n,k) is the number of strongly connected 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, 1, 1, 1, 2, 1, 6, 1, 10, 1, 19, 1, 28, 1, 1, 44, 2, 1, 60, 10, 1, 85, 31, 1, 110, 90, 1, 146, 222, 1, 182, 520, 1, 231, 1090, 1, 1, 280, 2180, 2, 1, 344, 4090, 11, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,7 COMMENTS Length of the n^th row: floor(sqrt(n)). These graphs are reflexive (each vertex has a self-loop), so T(n,k) = sum(A139621(n-k^2,m),m=0..k) T(n,1) = 1, T(n,2) = A005993(n-4), T(n,3) = A050927(n-9), T(n,4) = A050929(n-16). Row sums: A139630. LINKS EXAMPLE Triangle begins:   1   1   1   1  1   1  2   1  6   1 10   1 19   1 28  1 CROSSREFS Cf. A139623, A139624. Sequence in context: A191093 A266303 A267354 * A053785 A233809 A207536 Adjacent sequences:  A139622 A139623 A139624 * A139626 A139627 A139628 KEYWORD nonn,tabf AUTHOR Benoit Jubin, May 01 2008, Sep 01 2008 STATUS approved

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