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 A182517 Chromatic invariant of the square grid graph G_(n,n). 1
 1, 1, 3, 72, 11423, 11187798, 65460885384, 2247082682913972, 447548280314975144427, 513427482871084962707467332 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS The square grid graph G_(n,n) has n^2 = A000290(n) vertices and 2*n*(n-1) = A046092(n-1) edges. The chromatic invariant equals the absolute value of the first derivative of the chromatic polynomial evaluated at 1. 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 Cf. A000290, A046092, A182368 (chromatic polynomial). Sequence in context: A202948 A213986 A156908 * A135866 A307925 A006270 Adjacent sequences:  A182514 A182515 A182516 * A182518 A182519 A182520 KEYWORD nonn,more AUTHOR Alois P. Heinz, May 03 2012 EXTENSIONS a(10) from Andrew Howroyd, Apr 23 2018 STATUS approved

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Last modified July 29 23:58 EDT 2021. Contains 346346 sequences. (Running on oeis4.)