This site is supported by donations to The OEIS Foundation.

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A007869 Number of complementary pairs of graphs on n nodes. Also number of unlabeled graphs with n nodes and an even number of edges. 12
 1, 1, 2, 6, 18, 78, 522, 6178, 137352, 6002584, 509498932, 82545586656, 25251015686776, 14527077828617744, 15713242984902154384, 32000507852263779299344, 122967932076766466347469888, 893788862572805850273939095424, 12318904626562502262191503745716384 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Andrew Howroyd, Table of n, a(n) for n = 1..50 P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5. Nevena Francetić, Sarada Herke, Ian M. Wanless, Parity of Sets of Mutually Orthogonal Latin Squares, arXiv:1703.04764 [math.CO], 2017. See Section 4.1. Ferenc Szöllosi, The two-distance sets in dimension four, arXiv:1806.07861 [math.MG], 2018. See Table 1. FORMULA Average of A000088 and A000171. MATHEMATICA Needs["Combinatorica`"]; Table[Total[Table[NumberOfGraphs[n, m], {m, 0, Binomial[n, 2], 2}]], {n, 1, 15}]  (* Geoffrey Critzer, Oct 20 2012; modified by Harvey P. Dale, Aug 08 2013 *) CROSSREFS Cf. A000088, A000171. Cf. A054960 for graphs with an odd number of edges. Sequence in context: A113844 A266858 A141580 * A263915 A144557 A273001 Adjacent sequences:  A007866 A007867 A007868 * A007870 A007871 A007872 KEYWORD nonn,nice AUTHOR EXTENSIONS More terms from Vladeta Jovovic, Jul 19 2000 Terms a(18) and beyond from Andrew Howroyd, Sep 17 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 19 05:41 EST 2019. Contains 319304 sequences. (Running on oeis4.)