

A123547


Triangle read by rows: T(n,k) = number of unlabeled bicolored graphs with no isolated nodes having 2n nodes and k edges, with n nodes of each color. Here n >= 0, 0 <= k <= n^2.


3



1, 0, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 2, 4, 3, 2, 1, 1, 0, 0, 0, 0, 1, 2, 8, 14, 21, 20, 20, 12, 9, 4, 2, 1, 1, 0, 0, 0, 0, 0, 1, 2, 10, 31, 76, 137, 221, 285, 321, 301, 253, 182, 122, 69, 38, 19, 10, 4, 2, 1, 1, 0, 0, 0, 0, 0, 0, 1, 2, 11, 43, 162, 451, 1121, 2314, 4255, 6702
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OFFSET

0,13


COMMENTS

The colors may be interchanged.


REFERENCES

R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1978.


LINKS

R. W. Robinson, Rows 0 through 7, flattened
F. Harary, L. March and R. W. Robinson, On enumerating certain design problems in terms of bicolored graphs with no isolates, Environment and Planning, B 5 (1978), 3143.
F. Harary, L. March and R. W. Robinson, On enumerating certain design problems in terms of bicolored graphs with no isolates, Environment and Planning B: Urban Analytics and City Science, 5 (1978), 3143. [Annotated scanned copy]


CROSSREFS

Row sums give A007140. Cf. A007139, A106498 (gives beginning of this triangle).
Sequence in context: A109158 A307500 A049245 * A123551 A286275 A029717
Adjacent sequences: A123544 A123545 A123546 * A123548 A123549 A123550


KEYWORD

nonn,tabf


AUTHOR

N. J. A. Sloane, Nov 14 2006


STATUS

approved



