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A122078 Triangle read by rows: T(n,k) = number of unlabeled acyclic digraphs with n >= 0 nodes and n-k outnodes (0 <= k <= n). 2
1, 1, 1, 1, 1, 2, 3, 1, 3, 11, 16, 1, 4, 25, 108, 164, 1, 5, 47, 422, 2168, 3341, 1, 6, 78, 1251, 15484, 88747, 138101, 1, 7, 120, 3124, 79836, 1215783, 7409117, 11578037, 1, 8, 174, 6925, 333004, 11620961, 199203464, 1252610909 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,6

REFERENCES

R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.

LINKS

R. W. Robinson, Rows n=0 through n=15, flattened

EXAMPLE

Under P = K the entry ( S, K-S ) : R gives the number R of unlabeled acyclic digraphs on K nodes with exactly S outnodes:

P = 0

( 0, 0 ) : 1

Total( 0 ) : 1

P = 1

( 1, 0 ) : 1

Total( 1 ) : 1

P = 2

( 2, 0 ) : 1

( 1, 1 ) : 1

Total( 2 ) : 2

P = 3

( 3, 0 ) : 1

( 2, 1 ) : 2

( 1, 2 ) : 3

Total( 3 ) : 6

P = 4

( 4, 0 ) : 1

( 3, 1 ) : 3

( 2, 2 ) : 11

( 1, 3 ) : 16

Total( 4 ) : 31

P = 5

( 5, 0 ) : 1

( 4, 1 ) : 4

( 3, 2 ) : 25

( 2, 3 ) : 108

( 1, 4 ) : 164

Total( 5 ) : 302

P = 6

( 6, 0 ) : 1

( 5, 1 ) : 5

( 4, 2 ) : 47

( 3, 3 ) : 422

( 2, 4 ) : 2168

( 1, 5 ) : 3341

Total( 6 ) : 5984

CROSSREFS

Row sums give A003087.

Sequence in context: A065078 A203989 A126744 * A126736 A253257 A127412

Adjacent sequences:  A122075 A122076 A122077 * A122079 A122080 A122081

KEYWORD

nonn,tabl

AUTHOR

N. J. A. Sloane, Oct 18 2006

STATUS

approved

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Last modified September 21 23:55 EDT 2019. Contains 327286 sequences. (Running on oeis4.)