%I A123752
%S A123752 1,2,7,14,49,98,343,686,2401,4802,16807,33614,117649,235298,823543,
%T A123752 1647086,5764801,11529602,40353607,80707214,282475249,564950498,
%U A123752 1977326743,3954653486,13841287201,27682574402,96889010407,193778020814
%N A123752 a(n)=7a(n-2), a(0)=1, a(1)=2.
%F A123752 a(n)=7^(n/2)*[7(1+(-1)^n)+2sqrt(7)*(1-(-1)^n)]/14.
%F A123752 O.g.f.: (1+2x)/(1-7x^2). a(2n)=A000420(n). a(2n+1)=2*A000420(n). - R. 
               J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 18 2008
%p A123752 a[0]:=1: a[1]:=2: for n from 2 to 30 do a[n]:=7*a[n-2] od: seq(a[n],n=0..30);
%t A123752 f[0] = 1; f[1] = 2; f[n_] := f[n] = If[Mod[n, 2] == 1, 2*f[n - 1], (7/
               2)*f[n - 1]]; Table[f[n], {n, 0, 30}]
%Y A123752 Cf. A018592.
%Y A123752 Sequence in context: A128882 A018281 A018592 this_sequence A018622 A018668 
               A018684
%Y A123752 Adjacent sequences: A123749 A123750 A123751 this_sequence A123753 A123754 
               A123755
%K A123752 nonn
%O A123752 0,2
%A A123752 Roger Bagula and Gary Adamson (rlbagulatftn(AT)yahoo.com), Nov 15 2006
%E A123752 Edited by N. J. A. Sloane (njas(AT)research.att.com), Nov 29 2006