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%I #23 Feb 22 2020 20:29:09
%S 1,1,1,1,2,2,2,2,4,4,4,4,7,7,7,7,11,11,12,12,17,17,18,18,25,25,27,27,
%T 35,35,38,38,48,48,52,52,64,64,69,69,83,83,90,90,106,106,114,114,133,
%U 133,143,143,164,164,176,176,200,200,214,214,241,241,257,257,287,287,306,306,339
%N G.f.: (1+x^18)/((1-x)*(1-x^4)*(1-x^8)*(1-x^12)).
%H Alois P. Heinz, <a href="/A092508/b092508.txt">Table of n, a(n) for n = 0..1000</a>
%H G. Nebe, E. M. Rains and N. J. A. Sloane, <a href="http://neilsloane.com/doc/cliff2.html">Self-Dual Codes and Invariant Theory</a>, Springer, Berlin, 2006.
%H <a href="/index/Mo#Molien">Index entries for Molien series</a>
%H <a href="/index/Rec#order_25">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,1,-1,0,0,1,-1,0,0,0,0,0,0,-1,1,0,0,-1,1,0,0,1,-1).
%F a(n) ~ 1/1152*n^3. - _Ralf Stephan_, Apr 29 2014
%F G.f.: ( 1-x^6+x^12 ) / ( (1+x+x^2)*(1-x+x^2)*(x^4+1)*(x^2+1)^2*(1+x)^3*(x-1)^4 ). - _R. J. Mathar_, Dec 18 2014
%t CoefficientList[Series[(1+x^18)/((1-x)(1-x^4)(1-x^8)(1-x^12)),{x,0,100}],x] (* _Harvey P. Dale_, Dec 24 2019 *)
%o (PARI) a(n)=round((2*n^3+(21+3*(-1)^n)*n^2+(447+21*(-1)^n+108*(-1)^(n\2))*n+1393+223*(-1)^n)/2304) \\ _Tani Akinari_, May 30 2014
%K nonn
%O 0,5
%A _N. J. A. Sloane_, Apr 09 2004
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