A076323 Number of connected 4-colorable (i.e., chromatic number <= 4) simple graphs on n nodes.

1, 1, 2, 6, 20, 107, 801, 10227, 231228, 9708788, 743177051, 100580560531

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, A076322, A076324, A076325, A076326, A076327, A076328.

Cf. A076280, A076316, A084269, A126738.

Programs

Mathematica

A076316 = Cases[Import["https://oeis.org/A076316/b076316.txt", "Table"], {, }][[All, 2]];
(* EulerInvTransform is defined in A022562 *)
EulerInvTransform[A076316] (* Jean-François Alcover, Sep 25 2019, updated Mar 17 2020 *)

Formula

Inverse Euler transform of A076316. - Andrew Howroyd, Dec 02 2018

Extensions

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

a(12) from Sean A. Irvine, Apr 13 2025