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Search: id:A123548
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| A123548 |
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Triangle read by rows: T(n,k) = number of unlabeled bicolored graphs having 2n nodes and k edges, which are invariant when the two color classes are interchanged. Here n >= 0, 0 <= k <= n^2. |
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+0
1
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| 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 3, 2, 1, 1, 1, 1, 1, 1, 2, 4, 5, 7, 8, 9, 8, 7, 5, 4, 2, 1, 1, 1, 1, 1, 1, 2, 4, 6, 9, 14, 22, 29, 33, 37, 43, 43, 37, 33, 29, 22, 14, 9, 6, 4, 2, 1, 1, 1, 1, 1, 1, 2, 4, 6, 10, 16, 29, 46, 69, 99, 141, 183, 230, 277, 319, 342, 352, 342
(list; graph; listen)
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OFFSET
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0,12
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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, 1978.
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LINKS
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R. W. Robinson, Rows 0 through 7, flattened
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EXAMPLE
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Triangle begins:
n = 0
k = 0 : 1
************************ total ( 2n = 0) = 1
n = 1
k = 0 : 1
k = 1 : 1
************************ total ( 2n = 2) = 2
n = 2
k = 0 : 1
k = 1 : 1
k = 2 : 1
k = 3 : 1
k = 4 : 1
************************ total ( 2n = 4) = 5
n = 3
k = 0 : 1
k = 1 : 1
k = 2 : 1
k = 3 : 2
k = 4 : 3
k = 5 : 3
k = 6 : 2
k = 7 : 1
k = 8 : 1
k = 9 : 1
************************ total ( 2n = 6) = 16
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CROSSREFS
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Row sums give A122082.
Sequence in context: A099530 A167544 A074989 this_sequence A131838 A038529 A132312
Adjacent sequences: A123545 A123546 A123547 this_sequence A123549 A123550 A123551
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KEYWORD
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nonn,tabf
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Nov 14 2006
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