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%I #20 Dec 26 2016 16:07:07
%S 0,2,18,114,420,1170,2710,5538,10312,17890,29338,45970,69356,101362,
%T 144158,200258,272528,364226,479010,620978,794676,1005138,1257894,
%U 1559010,1915096,2333346,2821546,3388114,4042108,4793266,5652014
%N a(n) = (6*n^4 + 30*n^3 - 20*n^2 + 14)*n/30 + (n mod 2).
%H Harry J. Smith, <a href="/A064837/b064837.txt">Table of n, a(n) for n = 0..500</a>
%H G. L. Cohen and E. Tonkes, <a href="http://www.combinatorics.org/ojs/index.php/eljc/article/view/v8i2r4">Dartboard arrangements</a>, Elect. J. Combin., 8 (No. 2, 2001), #R4.
%H <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (5, -9, 5, 5, -9, 5, -1).
%F From _R. J. Mathar_, Dec 05 2008: (Start)
%F a(n) = 2*A064838(n).
%F G.f.: 2x*(1-x^5-2x^4+x^3+21x^2+4x)/((1-x)^6*(1+x)). (End)
%F a(0)=0, a(1)=2, a(2)=18, a(3)=114, a(4)=420, a(5)=1170, a(6)=2710, a(n) = 5*a(n-1) - 9*a(n-2) + 5*a(n-3) + 5*a(n-4) - 9*a(n-5) + 5*a(n-6) - a(n-7). - _Harvey P. Dale_, Sep 15 2014
%t Table[(6n^4+30n^3-20n^2+14) n/30+Mod[n,2],{n,0,30}] (* or *) LinearRecurrence[ {5,-9,5,5,-9,5,-1},{0,2,18,114,420,1170,2710},40] (* _Harvey P. Dale_, Sep 15 2014 *)
%o (PARI) { for (n=0, 500, a=(6*n^4 + 30*n^3 - 20*n^2 + 14)*n/30 + n%2; write("b064837.txt", n, " ", a) ) } \\ _Harry J. Smith_, Sep 28 2009
%K nonn
%O 0,2
%A _N. J. A. Sloane_, Oct 25 2001
%E Better description from _Frank Ellermann_, Mar 16 2002
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