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 A182553 Chromatic invariant of the complete tripartite graph K_(n,n,n). 2
 1, 11, 1243, 490043, 463370491, 860454250571, 2769263554592683, 14178247400433059003, 108483732651999512059291, 1182804548772797481324575531, 17700419121823142496192223238923, 352709466470858225716888461028622363, 9127611521817307582541815420363992765691 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The chromatic invariant equals the absolute value of the first derivative of the chromatic polynomial evaluated at 1. LINKS Alois P. Heinz, Table of n, a(n) for n = 1..60 Eric Weisstein's World of Mathematics, Chromatic Invariant Eric Weisstein's World of Mathematics, Complete Tripartite Graph Wikipedia, Chromatic Polynomial FORMULA a(n) = |(d/dq P(n,q))_{q=1}| with P(n,q) = Sum_{k,m=1..n} S2(n,k) * S2(n,m) * (q-k-m)^n * Product_{i=0..k+m-1} (q-i) and S2 = A008277. MAPLE with (combinat): P:= n-> expand (add (add (stirling2(n, k) *stirling2(n, m)          *mul(q-i, i=0..k+m-1) *(q-k-m)^n, m=1..n), k=1..n)): a:= n-> abs (subs (q=1, diff (P(n), q))): seq (a(n), n=1..15); CROSSREFS Cf. A008277, A048144. Sequence in context: A015009 A068326 A001323 * A223039 A209093 A078274 Adjacent sequences:  A182550 A182551 A182552 * A182554 A182555 A182556 KEYWORD nonn AUTHOR Alois P. Heinz, May 04 2012 STATUS approved

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Last modified May 22 03:34 EDT 2013. Contains 225511 sequences.