A006786 Number of squarefree graphs on n vertices.

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

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• more

References

• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• 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.

Extensions

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

2 more terms from Brendan McKay, Mar 11 2018