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A006786 Number of squarefree graphs on n vertices.
(Formerly M1149)
5
1, 2, 4, 8, 18, 44, 117, 351, 1230, 5069, 25181, 152045, 1116403, 9899865, 104980369, 1318017549, 19427531763, 333964672216, 6660282066936 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

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=1..19.

CombOS - Combinatorial Object Server, generate graphs

Brendan McKay, Emails to N. J. A. Sloane, 1991

B. D. McKay, Isomorph-free exhaustive generation, J Algorithms, 26 (1998) 306-324.

S. Uijlen, B. Westerbaan, A Kochen-Specker system has at least 22 vectors, arXiv preprint arXiv:1412.8544 [cs.DM], 2014.

S. Uijlen and B. Westerbaan, A Kochen-Specker System Has at Least 22 Vectors, New Generation Computing, Vol. 34, No. 1-2 (2016), 3-23.

Eric Weisstein's World of Mathematics, Square-Free Graph

CROSSREFS

Cf. A000088, A077269. Row sums of A300756.

Sequence in context: A100132 A176720 A088457 * A125809 A245176 A000117

Adjacent sequences:  A006783 A006784 A006785 * A006787 A006788 A006789

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane.

EXTENSIONS

2 more terms (from the McKay paper) from Vladeta Jovovic, May 17 2008

2 more terms from Brendan McKay, Mar 11 2018

STATUS

approved

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Last modified July 9 16:50 EDT 2020. Contains 335545 sequences. (Running on oeis4.)