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A084546
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Triangle read by rows: T(n,k) = C( C(n,2), k) for n >= 1, 0 <= k <= C(n,2).
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4
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1, 1, 1, 1, 3, 3, 1, 1, 6, 15, 20, 15, 6, 1, 1, 10, 45, 120, 210, 252, 210, 120, 45, 10, 1, 1, 15, 105, 455, 1365, 3003, 5005, 6435, 6435, 5005, 3003, 1365, 455, 105, 15, 1, 1, 21, 210, 1330, 5985, 20349, 54264, 116280, 203490, 293930, 352716, 352716, 293930, 203490, 116280, 54264, 20349, 5985, 1330, 210, 21, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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COMMENTS
| T(n,k) gives number of labeled simple graphs with n nodes and k edges.
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REFERENCES
| J. L. Gross and J. Yellen, eds., Handbook of Graph Theory, CRC Press, 2004; p. 517.
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EXAMPLE
| Triangle begins
1;
1,1;
1,3,3,1;
1,6,15,20,15,6,1; ...
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MATHEMATICA
| Table[Table[Binomial[Binomial[n, 2], k], {k, 0, Binomial[n, 2]}], {n, 1, 7}]//Grid (* Geoffrey Critzer, Apr 28 2011 *)
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CROSSREFS
| Cf. A083029. A subset of the rows of Pascal's triangle A007318.
Sequence in context: A080858 A144228 A083029 * A174116 A026515 A075772
Adjacent sequences: A084543 A084544 A084545 * A084547 A084548 A084549
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KEYWORD
| nonn,tabf
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jul 13 2003
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