A055156 Powers of 3 which are not powers of 3^3.

3, 9, 81, 243, 2187, 6561, 59049, 177147, 1594323, 4782969, 43046721, 129140163, 1162261467, 3486784401, 31381059609, 94143178827, 847288609443, 2541865828329, 22876792454961, 68630377364883, 617673396283947

Offset

0,1

Links

Table of n, a(n) for n=0..20.

Index entries for linear recurrences with constant coefficients, signature (0, 27).

Formula

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).

Mathematica

With[{nn=40}, Complement[3^Range[nn], 27^Range[Floor[nn/3]]]] (* or *) LinearRecurrence[{0, 27}, {3, 9}, 40] (* Harvey P. Dale, Jul 17 2012 *)

Crossrefs

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: A124049 A067623 A171557 * A047912 A078684 A121858

Adjacent sequences: A055153 A055154 A055155 * A055157 A055158 A055159

Keyword

nonn,easy

Author

Henry Bottomley, Jun 20 2000

Status

approved