0,1

a(n) = a(n-1)*a(n-2)/a(n-3) = 27*a(n-2) = 3^A001651(n). a(2n) = 3^(3n+1), a(2n+1) = 3^(3n+2).

Cf. A013732 and A013733. Consists of numbers in A000244 which are not in A009971. See A004171 for powers of 2 which are not powers of 2^2.

Sequence in context: A139731 A124049 A067623 this_sequence A047912 A078684 A121858

Adjacent sequences: A055153 A055154 A055155 this_sequence A055157 A055158 A055159

easy,nonn

Henry Bottomley (se16(AT)btinternet.com), Jun 20 2000