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Search: id:A058876
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| A058876 |
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Triangle T(n,k) = number of labeled acyclic digraphs with n nodes, containing exactly k points of in-degree zero (n >= 1, 1<=k<=n). |
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+0
6
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| 1, 1, 2, 1, 9, 15, 1, 28, 198, 316, 1, 75, 1610, 10710, 16885, 1, 186, 10575, 211820, 1384335, 2174586, 1, 441, 61845, 3268125, 64144675, 416990763, 654313415, 1, 1016, 336924, 43832264, 2266772550, 44218682312, 286992935964, 450179768312
(list; table; graph; listen)
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OFFSET
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1,3
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REFERENCES
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F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 19, (1.6.4).
R. W. Robinson, Counting labeled acyclic digraphs, pp. 239-273 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973.
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FORMULA
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H. and P. (following Robinson) give a recurrence
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EXAMPLE
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1; 1,2; 1,9,15; 1,28,198,316; ...
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CROSSREFS
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Columns give A058877, A003025, A003026. Row sums give A003024.
Sequence in context: A099599 A085488 A072265 this_sequence A083162 A094633 A144244
Adjacent sequences: A058873 A058874 A058875 this_sequence A058877 A058878 A058879
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KEYWORD
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nonn,easy,tabl
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Jan 07 2001
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EXTENSIONS
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More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 10 2001
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