%I A138340
%S A138340 1,4,32,64,256,2048,4096,16384,131072,262144,1048576,8388608,16777216,
%T A138340 67108864,536870912,1073741824,4294967296,34359738368,68719476736,
%U A138340 274877906944,2199023255552,4398046511104,17592186044416
%V A138340 1,-4,-32,-64,256,2048,4096,-16384,-131072,-262144,1048576,8388608,16777216,
               -67108864,
%W A138340 -536870912,-1073741824,4294967296,34359738368,68719476736,-274877906944,
%X A138340 -2199023255552,-4398046511104,17592186044416
%N A138340 Expansion of (1-8x)/(1-4x+16x^2).
%C A138340 abs(a(n))=2^A047267(n).
%F A138340 a(n):=2*4^n(cos(pi*(n+1)/3)-sqrt(3)*sin(pi*(n+1))/3);
%F A138340 a(n)=4^n*Sum_{k, 0<=k<=n} A121314(n,k)*(-1)^k*3^(n-k). [From Philippe 
               DELEHAM (kolotoko(AT)wanadoo.fr), Nov 01 2008]
%F A138340 a(n)=A128018(n)*2^n. [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), 
               Nov 14 2008]
%Y A138340 Sequence in context: A114076 A078092 A076137 this_sequence A113250 A012036 
               A153794
%Y A138340 Adjacent sequences: A138337 A138338 A138339 this_sequence A138341 A138342 
               A138343
%K A138340 easy,sign
%O A138340 0,2
%A A138340 Paul Barry (pbarry(AT)wit.ie), Mar 15 2008