A325447 Triangle read by rows: T(n,k) is the number of simple nonseparable (or 2-connected) graphs on n unlabeled nodes with circumference k, (n >= 3, k >= 3).

1, 0, 3, 0, 2, 8, 0, 2, 6, 48, 0, 2, 9, 74, 383, 0, 2, 10, 159, 756, 6196, 0, 2, 13, 276, 2058, 14634, 177083, 0, 2, 14, 505, 4824, 48137, 384942, 9305118

Offset: 3

Author

Andrew Howroyd, Sep 06 2019

Keywords

• nonn
• tabl
• more

Examples

			Triangle begins, (n >= 3, k >= 3):
  1;
  0, 3;
  0, 2,  8;
  0, 2,  6,  48;
  0, 2,  9,  74,  383;
  0, 2, 10, 159,  756,  6196;
  0, 2, 13, 276, 2058, 14634, 177083;
  0, 2, 14, 505, 4824, 48137, 384942, 9305118;
  ...
		

Links

• Eric Weisstein's World of Mathematics, Graph Circumference
• Eric Weisstein's World of Mathematics, Hamiltonian Graph

Crossrefs

Row sums are A002218(n >= 3).

Right diagonal is A003216.

Cf. A128042, A325455.

Formula

T(n, 4) = 2 for n > 4.