OFFSET
1,3
COMMENTS
LINKS
Eric Weisstein's World of Mathematics, Chromatic Invariant
Eric Weisstein's World of Mathematics, Grid Graph
Wikipedia, Chromatic Polynomial
FORMULA
a(n) = |(d/dq P(n,q))_{q=1}| with P(n,q) = Sum_{k=0..n^2} A182368(n,k) * q^(n^2-k).
MATHEMATICA
Abs[Table[Derivative[1][ChromaticPolynomial[GridGraph[{n, n}]]][1], {n, 7}]] (* Eric W. Weisstein, May 01 2017 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Alois P. Heinz, May 03 2012
EXTENSIONS
a(10) from Andrew Howroyd, Apr 23 2018
STATUS
approved