login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Table of n, a(n) for n=1..47.

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

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