A076322 Number of connected 3-colorable (i.e., chromatic number <= 3) simple graphs on n nodes.

1, 1, 2, 5, 17, 81, 519, 5218, 81677, 2014360, 76140741, 4303246908

Offset: 1

Author

Eric W. Weisstein, Oct 06 2002

Keywords

• nonn
• more

Links

• Maria Chudnovsky, Jan Goedgebeur, Oliver Schaudt, Mingxian Zhong, Obstructions for three-coloring graphs without induced paths on six vertices, arXiv preprint, arXiv:1504.06979 [math.CO], 2015-2018.
• Eric Weisstein's World of Mathematics, n-Colorable Graph

Crossrefs

Cf. A005142, A076323, A076324, A076325, A076326, A076327, A076328.

Cf. A076279, A076315, A084269, A126737.

Programs

Mathematica

A076315 = Cases[Import["https://oeis.org/A076315/b076315.txt", "Table"], {, }][[All, 2]];
(* EulerInvTransform is defined in A022562 *)
EulerInvTransform[A076315] (* Jean-François Alcover, Sep 25 2019, updated Mar 17 2020 *)

Formula

Inverse Euler transform of A076315. - Andrew Howroyd, Dec 02 2018

Extensions

a(10)-a(11) from Andrew Howroyd, Dec 02 2018

a(12) from Jinyuan Wang, Feb 23 2020