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A280333 Chromatic invariant of the n-Andrásfai graph. 0
1, 1, 12, 815, 157762, 64916201, 48508522364 (list; graph; refs; listen; history; text; internal format)
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: A305935 A228182 A003748 * A207817 A203410 A275568

Adjacent sequences:  A280330 A280331 A280332 * A280334 A280335 A280336

KEYWORD

nonn,hard,more

AUTHOR

Eric M. Schmidt, Dec 31 2016

STATUS

approved

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Last modified October 26 17:32 EDT 2020. Contains 338027 sequences. (Running on oeis4.)