A210717 Number of disconnected regular simple graphs on n vertices with girth exactly 7.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 3, 4, 4, 5, 6, 7, 8, 10, 11, 13, 15, 18, 20, 24, 27, 32, 36, 42, 48, 56, 63, 73, 83, 96, 109, 125, 144, 162, 210, 209, 845, 270, 32541, 346, 1885800, 443, 101215159, 565, 5025321572

Offset: 0

Author

Jason Kimberley, Dec 18 2012

Keywords

• nonn
• more
• hard

Links

• Jason Kimberley, Index of sequences counting disconnected k-regular simple graphs with girth exactly g

Formula

a(n) = A185217(n) - A185218(n).