A186714 Triangular array C(n, k) = number of connected k-regular graphs, having girth at least 4, with n nodes, 0 <= k <= n div 2.

1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 2, 1, 0, 0, 1, 0, 0, 0, 0, 1, 6, 2, 1, 0, 0, 1, 0, 2, 0, 0, 0, 1, 22, 12, 1, 1, 0, 0, 1, 0, 31, 0, 0, 0, 0, 1, 110, 220, 7, 1, 1, 0, 0, 1, 0, 1606, 0, 1, 0, 0, 0, 1, 792, 16828, 388, 9, 1, 1, 0, 0, 1, 0, 193900, 0, 6, 0, 0, 0, 0, 1

Offset: 1

Author

Jason Kimberley, Sep 04 2011

Keywords

• nonn
• tabf
• hard

Examples

			01: 1;
02: 0,1;
03: 0,0;
04: 0,0,1;
05: 0,0,1;
06: 0,0,1,1;
07: 0,0,1,0;
08: 0,0,1,2,1;
09: 0,0,1,0,0;
10: 0,0,1,6,2,1;
11: 0,0,1,0,2,0;
12: 0,0,1,22,12,1,1;
13: 0,0,1,0,31,0,0;
14: 0,0,1,110,220,7,1,1;
15: 0,0,1,0,1606,0,1,0;
16: 0,0,1,792,16828,388,9,1,1;
17: 0,0,1,0,193900,0,6,0,0;
18: 0,0,1,7805,2452818,406824,267,8,1,1;
19: 0,0,1,0,32670330,0,3727,0,0,0;
20: 0,0,1,97546,456028474,1125022325,483012,741,13,1,1;
21: 0,0,1,0,6636066099,0,69823723,0,1,0,0;
22: 0,0,1,1435720,100135577747,3813549359274,14836130862,2887493,?,14,1,1;
23: 0,0,1,0,1582718912968,0,?,0,?,0,0;
		

Links

• Jason Kimberley, Connected regular graphs with girth at least 4
• Jason Kimberley, Index of sequences counting connected k-regular simple graphs with girth at least g

Crossrefs

The sum of the n-th row is A186724(n).

Connected k-regular simple graphs with girth at least 4: A186724 (any k), this sequence (triangle); specified degree k: A185114 (k=2), A014371 (k=3), A033886 (k=4), A058275 (k=5), A058276 (k=6), A181153 (k=7), A181154 (k=8), A181170 (k=9).

Triangular arrays C(n,k) counting connected simple k-regular graphs on n vertices with girth *at least* g: A068934 (g=3), this sequence (g=4), A186715 (g=5), A186716 (g=6), A186717 (g=7), A186718 (g=8), A186719 (g=9).

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