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%I #27 Sep 08 2022 08:45:13
%S 1,1,1,1,2,2,2,2,4,4,4,4,6,6,6,6,8,8,8,8,10,10,10,10,12,12,12,12,14,
%T 14,14,14,16,16,16,16,18,18,18,18,20,20,20,20,22,22,22,22,24,24,24,24,
%U 26,26,26,26,28,28,28,28,30,30,30,30,32,32,32,32,34,34,34,34,36,36,36,36,38,38
%N G.f.: (1+x^8)/((1-x)*(1-x^4)).
%H Vincenzo Librandi, <a href="/A092533/b092533.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_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,1,-1).
%F a(n) = 1 for n<4, a(n) = 2*floor(n/4) for n>=4. - _Ralf Stephan_, Apr 29 2014
%t CoefficientList[Series[(1+x^8)/((1-x)(1-x^4)),{x,0,100}],x] (* or *) Join[{1,1,1,1},LinearRecurrence[{1,0,0,1,-1},{2,2,2,2,4},80]] (* _Harvey P. Dale_, Jul 25 2014 *)
%o (Magma) I:=[1,1,1,1,2,2,2,2,4]; [n le 9 select I[n] else Self(n-1)+Self(n-4)-Self(n-5): n in [1..30]]; // _Vincenzo Librandi_, Jul 25 2014
%K nonn,easy
%O 0,5
%A _N. J. A. Sloane_, Apr 08 2004
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