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A006648 Number of graphs with n nodes, n-1 edges and no isolated vertices.
(Formerly M1181)
0
1, 1, 2, 4, 9, 20, 50, 124, 332, 895, 2513, 7172, 20994, 62366, 188696, 578717, 1799999, 5666257, 18047319, 58097540, 188953756, 620493315, 2056582095, 6877206111, 23195975865, 78891742748, 270505303760, 934890953041, 3256230606767 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,3

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

Table of n, a(n) for n=2..30.

FORMULA

a(n) = A001433(n) - A001434(n - 1). - Sean A. Irvine, Jun 06 2017

CROSSREFS

Cf. A001433, A001434.

Sequence in context: A093637 A068051 A032289 * A128496 A134955 A171887

Adjacent sequences:  A006645 A006646 A006647 * A006649 A006650 A006651

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Vladeta Jovovic, Mar 02 2008

More terms from Sean A. Irvine, Jun 06 2017

STATUS

approved

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Last modified February 22 15:12 EST 2018. Contains 299454 sequences. (Running on oeis4.)