A280333 Chromatic invariant of the n-Andrásfai graph.

1, 1, 12, 815, 157762, 64916201, 48508522364

Offset

1,3

Links

Table of n, a(n) for n=1..7.

Eric Weisstein's World of Mathematics, Andrásfai Graph

Eric Weisstein's World of Mathematics, Chromatic Invariant

Mathematica

Table[Derivative[1][ChromaticPolynomial[CirculantGraph[3 n - 1, Range[1, 3 n, 3]]]][1], {n, 6}] // Abs (* Eric W. Weisstein, Apr 11 2017 *)

Prog

(Sage) def a(n) : return graphs.CirculantGraph(3*n-1, range(1, 3*n, 3)) .chromatic_polynomial().derivative()(1).abs()

Crossrefs

Cf. A193126.

Sequence in context: A228182 A356186 A003748 * A350412 A207817 A349468

Adjacent sequences: A280330 A280331 A280332 * A280334 A280335 A280336

Keyword

nonn,hard,more

Author

Eric M. Schmidt, Dec 31 2016

Status

approved