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

Author

Henry Bottomley, Jun 20 2000

Keywords

• nonn
• easy

Links

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

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.

Programs

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 *)

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).