A185315 Number of, not necessarily connected, regular simple graphs on n vertices with girth at least 5.

1, 1, 2, 1, 2, 2, 3, 2, 3, 2, 5, 3, 7, 4, 15, 6, 57, 8, 466, 12, 5801, 24, 91091, 3939, 1744378, 4132022, 163639295, 4018022192, 119026596500

Offset: 0

Author

Jason Kimberley, Dec 12 2012

Keywords

• nonn
• more
• hard

Links

• Jason Kimberley, Index of sequences counting not necessarily connected k-regular simple graphs with girth at least g

Crossrefs

Not necessarily connected k-regular simple graphs with girth at least 5: this sequence (any k), A185305 (triangle); specified degree k: A185325 (k=2), A185335 (k=3).

Not necessarily connected regular simple graphs with girth at least g: A005176 (g=3), A185314 (g=4), this sequence (g=5), A185316 (g=6), A185317 (g=7), A185318 (g=8), A185319 (g=9).

Formula

a(n) = A186725(n) + A185215(n).