login
A360862
Triangle read by rows: T(n,k) is the number of unlabeled connected multigraphs with n edges on k nodes and degree >= 3 at each node, loops allowed, n >= 2, 1 <= k <= floor(2*n/3).
4
1, 1, 2, 1, 4, 1, 7, 5, 1, 10, 20, 5, 1, 14, 48, 36, 1, 18, 99, 153, 30, 1, 23, 181, 481, 277, 17, 1, 28, 303, 1239, 1451, 323, 1, 34, 479, 2811, 5572, 2946, 193, 1, 40, 726, 5805, 17607, 17343, 3806, 71, 1, 47, 1055, 11148, 48401, 77708, 36872, 3188, 1, 54, 1492, 20219, 120018, 288476, 243007, 54386, 1496
OFFSET
2,3
COMMENTS
Terms may be computed using the tools geng, vcolg and multig in nauty with some additional processing to check the degrees of nodes.
LINKS
Brendan McKay and Adolfo Piperno, nauty and Traces
EXAMPLE
Triangle begins:
1;
1, 2;
1, 4;
1, 7, 5;
1, 10, 20, 5;
1, 14, 48, 36;
1, 18, 99, 153, 30;
1, 23, 181, 481, 277, 17;
1, 28, 303, 1239, 1451, 323;
1, 34, 479, 2811, 5572, 2946, 193;
1, 40, 726, 5805, 17607, 17343, 3806, 71;
1, 47, 1055, 11148, 48401, 77708, 36872, 3188;
1, 54, 1492, 20219, 120018, 288476, 243007, 54386, 1496;
...
CROSSREFS
Column 2 is A014616.
Row sums are A360863.
Diagonal sums are A360864.
Cf. A322115, A327615, A360866 (loopless).
Sequence in context: A115124 A115122 A097360 * A325348 A307683 A248058
KEYWORD
nonn,tabf
AUTHOR
Andrew Howroyd, Feb 24 2023
STATUS
approved