A006649 Number of graphs with n nodes, n edges and no isolated vertices.

1, 0, 0, 1, 2, 5, 15, 41, 124, 369, 1132, 3491, 10984, 34768, 111514, 360560, 1176797, 3870389, 12829765, 42829894, 143980892, 487227611, 1659499566, 5688046485, 19617965938, 68078878268, 237694501644, 834946053269, 2950683815028, 10490767818951, 37524169403930

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn

References

• W. L. Kocay, Some new methods in reconstruction theory, pp. 89 - 114 of Combinatorial Mathematics IX. Proc. Ninth Australian Conference (Brisbane, August 1981). Ed. E. J. Billington, S. Oates-Williams and A. P. Street. Lecture Notes Math., 952. Springer-Verlag, 1982.
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Andrew Howroyd, Table of n, a(n) for n = 0..50

Crossrefs

Cf. A001434, A008406, A048179, A368599.

Programs

PARI

a(n) = polcoef(G(n, O(x*x^n)) - if(n, G(n-1, O(x*x^n))), n) \\ G defined in A008406. - Andrew Howroyd, Jan 09 2024

Formula

a(n) = A008406(n,n) - A008406(n-1, n) for n > 0. - Andrew Howroyd, Jan 09 2024

Extensions

More terms from Vladeta Jovovic, Mar 02 2008

a(0)-a(2) prepended and a(27) and beyond from Andrew Howroyd, Jan 09 2024