A360866 Triangle read by rows: T(n,k) is the number of unlabeled connected loopless multigraphs with n edges on k nodes and degree >= 3 at each node, n >= 2, 1 <= k <= floor(2*n/3).
0, 0, 1, 0, 1, 0, 1, 1, 0, 1, 3, 2, 0, 1, 4, 7, 0, 1, 6, 19, 6, 0, 1, 8, 40, 37, 6, 0, 1, 10, 71, 135, 56, 0, 1, 12, 117, 366, 338, 35, 0, 1, 15, 184, 858, 1417, 494, 20, 0, 1, 17, 270, 1778, 4670, 3494, 492, 0, 1, 20, 387, 3413, 13125, 17355, 6047, 251
Offset: 2
Examples
Triangle begins: 0; 0, 1; 0, 1; 0, 1, 1; 0, 1, 3, 2; 0, 1, 4, 7; 0, 1, 6, 19, 6; 0, 1, 8, 40, 37, 6; 0, 1, 10, 71, 135, 56; 0, 1, 12, 117, 366, 338, 35; 0, 1, 15, 184, 858, 1417, 494, 20; 0, 1, 17, 270, 1778, 4670, 3494, 492; 0, 1, 20, 387, 3413, 13125, 17355, 6047, 251; ...
Links
- Brendan McKay and Adolfo Piperno, nauty and Traces.
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