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A106498
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Triangle read by rows: T(n,k) = number of unlabeled bicolored graphs with isolated nodes allowed having 2n nodes and k edges, with n nodes of each color. Here n >= 0, 0 <= k <= n^2.
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2
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1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 4, 5, 5, 4, 2, 1, 1, 1, 1, 2, 4, 10, 13, 23, 26, 32, 26, 23, 13, 10, 4, 2, 1, 1, 1, 1, 2, 4, 10, 20, 39, 72, 128, 198, 280, 353, 399, 399, 353, 280, 198, 128, 72, 39, 20, 10, 4, 2, 1, 1, 1, 1, 2, 4, 10, 20, 50, 99, 227, 458, 934, 1711
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,6
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COMMENTS
| The colors may be interchanged.
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REFERENCES
| R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1978.
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LINKS
| R. W. Robinson, Rows 0 through 7, flattened
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EXAMPLE
| Triangles A106498 and A123547 begin:
n = 0
k = 0 : 1, 1
Total = 1, 1
n = 1
k = 0 : 1, 0
k = 1 : 1, 1
Total = 2, 1
n = 2
k = 0 : 1, 0
k = 1 : 1, 0
k = 2 : 2, 1
k = 3 : 1, 1
k = 4 : 1, 1
Totals = 6, 3
n = 3
k = 0 : 1, 0
k = 1 : 1, 0
k = 2 : 2, 0
k = 3 : 4, 1
k = 4 : 5, 2
k = 5 : 5, 4
k = 6 : 4, 3
k = 7 : 2, 2
k = 8 : 1, 1
k = 9 : 1, 1
Totals = 26, 14
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CROSSREFS
| Row sums give A007139. Cf. A122081, A123547.
Sequence in context: A063746 A201075 A131338 * A093466 A125761 A060990
Adjacent sequences: A106495 A106496 A106497 * A106499 A106500 A106501
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KEYWORD
| nonn,tabf
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Nov 14 2006
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