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%I #7 Jun 13 2015 00:51:30
%S 1,4,4,13,49,85,202,643,1408,3226,9013,21685,50719,131836,327001,
%T 783472,1969996,4913005,11964253,29694217,73911262,181589539,
%U 448837492,1114038850,2748344701,6787882129,16814231779,41549334088,102640273249
%N Sum k=0..n, C(n-k, floor(k/2))3^k.
%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,9)
%F G.f. : (1+3x)/(1-x-9x^3); a(n)=a(n-1)+9a(n-3).
%Y Cf. A097333, A097334, A097336.
%K easy,nonn
%O 0,2
%A _Paul Barry_, Aug 05 2004
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