cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A122083 Triangle read by rows in which row n gives the number of unlabeled bicolored graphs having k nodes of one color and n-k nodes of the other color, with no isolated nodes; the color classes are not interchangeable.

Original entry on oeis.org

1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 3, 1, 0, 0, 1, 5, 5, 1, 0, 0, 1, 8, 17, 8, 1, 0, 0, 1, 11, 42, 42, 11, 1, 0, 0, 1, 15, 91, 179, 91, 15, 1, 0, 0, 1, 19, 180, 633, 633, 180, 19, 1, 0, 0, 1, 24, 328, 2001, 3835, 2001, 328, 24, 1, 0, 0, 1, 29, 565, 5745, 20755, 20755
Offset: 0

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Author

N. J. A. Sloane, Oct 19 2006

Keywords

Examples

			K M N Gives the number N of unlabeled bicolored graphs with no isolated nodes and having K nodes of one color and M nodes of the other color.
0 0 1
Total( 0)= 1
0 1 0
1 0 0
Total( 1)= 0
0 2 0
1 1 1
2 0 0
Total( 2)= 1
0 3 0
1 2 1
2 1 1
3 0 0
Total( 3)= 2
0 4 0
1 3 1
2 2 3
3 1 1
4 0 0
Total( 4)= 5
0 5 0
1 4 1
2 3 5
3 2 5
4 1 1
5 0 0
Total( 5)= 12
0 6 0
1 5 1
2 4 8
3 3 17
4 2 8
5 1 1
6 0 0
Total( 6)= 35
		

References

  • J. G. Lee, Almost Distributive Lattice Varieties, Algebra Universalis, 21 (1985), 280-304.
  • R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.

Crossrefs

Row sums give A055192. See A056152 for a version of this triangle with the bounding zeros in each row.