A006649 Number of graphs with n nodes, n edges and no isolated vertices. (Formerly M1474)

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

0,5

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

Formula

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

Prog

(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

Crossrefs

Cf. A001434, A008406, A048179, A368599.

Sequence in context: A148349 A076865 A190140 * A303980 A148350 A304201

Adjacent sequences: A006646 A006647 A006648 * A006650 A006651 A006652

Keyword

nonn

Author

N. J. A. Sloane

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

Status

approved