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%I #12 Apr 23 2018 10:31:56
%S 1,11,328,16369,1181276,116093641,14916610346,2428960220241,
%T 489039354264712,119323954705155265,34701518665828422926,
%U 11861024763916090258105,4708209994260510940754540,2148158302978435764574475817,1116465105383647067485461486754
%N Chromatic invariant of the n-crown graph.
%H Andrew Howroyd, <a href="/A295171/b295171.txt">Table of n, a(n) for n = 3..100</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ChromaticInvariant.html">Chromatic Invariant</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/CrownGraph.html">Crown Graph</a>
%F a(n) = Sum_{k=2..2*n} Sum_{j=0..n} Sum_{i=0..k-j} (-1)^k*(k-2)!*binomial(n, j)*Stirling2(n-j, i)*Stirling2(n-j, k-j-i). - _Andrew Howroyd_, Apr 22 2018
%t Table[Sum[(-1)^k (k - 2)! Binomial[n, j] StirlingS2[n - j, i] StirlingS2[n - j, k - j - i], {k, 2, 2 n}, {j, 0, n}, {i, 0, k - j}], {n, 3, 20}] (* _Eric W. Weisstein_, Apr 23 2018 *)
%o (PARI) a(n)={sum(k=2, 2*n, (-1)^k*(k-2)!*sum(j=0, min(n,k), binomial(n, j)*sum(i=0, k-j, stirling(n-j, i, 2)*stirling(n-j, k-j-i, 2))))} \\ _Andrew Howroyd_, Apr 22 2018
%K nonn
%O 3,2
%A _Eric W. Weisstein_, Nov 16 2017
%E Terms a(10) and beyond from _Andrew Howroyd_, Apr 22 2018
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