A006786 Number of squarefree graphs on n vertices. (Formerly M1149)

1, 2, 4, 8, 18, 44, 117, 351, 1230, 5069, 25181, 152045, 1116403, 9899865, 104980369, 1318017549, 19427531763, 333964672216, 6660282066936

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

Index entries for sequences of squarefree graphs

Crossrefs

Cf. A000088, A077269 (connected), A345249 (labeled), A039751 (complement). 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