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Search: id:A122078
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| A122078 |
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Triangle read by rows: T(n,k) = number of unlabeled acyclic digraphs with n >= 0 nodes and n-k outnodes (0 <= k <= n). |
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2
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| 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; listen)
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OFFSET
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0,6
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REFERENCES
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R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.
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LINKS
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R. W. Robinson, Rows n=0 through n=15, flattened
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EXAMPLE
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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
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CROSSREFS
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Row sums give A003087.
Sequence in context: A145080 A065078 A126744 this_sequence A126736 A127412 A152832
Adjacent sequences: A122075 A122076 A122077 this_sequence A122079 A122080 A122081
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KEYWORD
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nonn,tabl
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Oct 18 2006
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