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A057278 Triangle T(n,k) of number of digraphs with a source and a sink on n unlabeled nodes and k arcs, k=0,1,..,n*(n-1). 2
1, 0, 1, 1, 0, 0, 1, 4, 4, 1, 1, 0, 0, 0, 1, 11, 31, 45, 38, 27, 13, 5, 1, 1, 0, 0, 0, 0, 1, 23, 152, 486, 992, 1419, 1641, 1485, 1152, 707, 379, 154, 61, 16, 5, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,8

REFERENCES

V. Jovovic, G. Kilibarda, Enumeration of labeled initially-finally connected digraphs, Scientific review, Serbian Scientific Society, 19-20 (1996), p. 246.

LINKS

Table of n, a(n) for n=1..45.

EXAMPLE

[1],[0,1,1],[0,0,1,4,4,1,1],[0,0,0,1,11,31,45,38,27,13,5,1,1],...; Number of digraphs with a source and a sink on 3 unlabeled nodes is 11=1+4+4+1+1.

CROSSREFS

Row sums give A049531. Cf. A057270-A057277, A057279.

Sequence in context: A164612 A180401 A057270 * A010303 A046553 A046552

Adjacent sequences:  A057275 A057276 A057277 * A057279 A057280 A057281

KEYWORD

more,nonn,tabf

AUTHOR

Vladeta Jovovic, Goran Kilibarda, Sep 14 2000

STATUS

approved

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Last modified February 17 10:59 EST 2019. Contains 320219 sequences. (Running on oeis4.)