a(n) = 4^(2*n+1).A013709a(n) = 4^(2*n+1).Terms a(0) =4a(1) =64a(2) =1024a(3) =16384a(4) =262144a(5) =4194304a(6) =67108864a(7) =1073741824a(8) =17179869184a(9) =274877906944External referencesoeis: A013709