A198315 Number of, not necessarily connected, regular simple graphs on n vertices with girth exactly 5.

0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 2, 1, 3, 1, 9, 2, 50, 3, 453, 5, 5759, 14, 90693, 3926, 1736786, 4132004, 163458044, 4018022167, 119021971966

Offset: 0

Author

Jason Kimberley, Dec 13 2012

Keywords

• nonn
• more
• hard

Links

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

Crossrefs

Not necessarily connected regular simple graphs girth exactly g: A198313 (g=3), A198314 (g=4), this sequence (g=5), A198316 (g=6), A198317 (g=7), A198318 (g=8).

Formula

a(n) = A186745(n) + A210715(n).

a(n) = A185315(n) - A185316(n).