A186717 Irregular triangle C(n,k): the number of connected k-regular graphs on n vertices having girth at least seven.

1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 3, 0, 0, 1, 0, 0, 0, 1, 21, 0, 0, 1, 0, 0, 0, 1, 546, 0, 0, 1, 0, 0, 0, 1, 30368

Offset: 1

Author

Jason Kimberley, Nov 28 2011

Keywords

• nonn
• hard
• tabf

Examples

			1;
0, 1;
0, 0;
0, 0;
0, 0;
0, 0;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1;
0, 0, 1, 1;
0, 0, 1, 0;
0, 0, 1, 3;
0, 0, 1, 0;
0, 0, 1, 21;
0, 0, 1, 0;
0, 0, 1, 546;
0, 0, 1, 0;
0, 0, 1, 30368;
0, 0, 1, 0;
0, 0, 1, 1782840;
0, 0, 1, 0;
0, 0, 1, 95079083;
0, 0, 1, 0;
0, 0, 1, 4686063120;
0, 0, 1, 0;
		

Links

• Jason Kimberley, Table of i, a(i) for i = 1..126 (n = 1..39)
• Jason Kimberley, Connected regular graphs with girth at least 7
• Jason Kimberley, Index of sequences counting connected k-regular simple graphs with girth at least g

Crossrefs

Triangular arrays C(n,k) counting connected simple k-regular graphs on n vertices with girth at least g: A068934 (g=3), A186714 (g=4), A186715 (g=5), A186716 (g=6), this sequence (g=7), A186718 (g=8), A186719 (g=9).

Connected k-regular simple graphs with girth at least 7: A186727 (any k), this sequence (triangle); specific k: A185117 (k=2), A014375 (k=3).

Triangular arrays C(n,k) counting connected simple k-regular graphs on n vertices with girth exactly g: A186733 (g=3), A186734 (g=4).