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%I #6 Jun 13 2015 00:51:32
%S 1,2,4,10,28,80,228,648,1840,5224,14832,42112,119568,339488,963904,
%T 2736800,7770560,22062848,62642752,177860736,504997632,1433833088,
%U 4071063296,11558916096,32819077376,93182771712,264572609536
%N a(n)=4a(n-1)-4a(n-2)+2a(n-3).
%C Binomial transform of tribonacci numbers A000213.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (4,-4,2).
%F G.f.: (1-2x)/((1-2x)^2-2x^3); a(n)=sum{k=0..floor(n/3), binomial(n-k, 2k)2^k*2^(n-3k)}.
%Y Cf. A099214, A099215, A055588.
%K easy,nonn
%O 0,2
%A _Paul Barry_, Oct 06 2004
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