A166450 a(n) = 3*a(n-2) for n > 2; a(1) = 1, a(2) = 6.

1, 6, 3, 18, 9, 54, 27, 162, 81, 486, 243, 1458, 729, 4374, 2187, 13122, 6561, 39366, 19683, 118098, 59049, 354294, 177147, 1062882, 531441, 3188646, 1594323, 9565938, 4782969, 28697814, 14348907, 86093442, 43046721, 258280326

Offset: 1

Author

Klaus Brockhaus, Oct 13 2009

Keywords

• nonn
• easy

Comments

Interleaving of A000244 and 6*A000244.

Second binomial transform is A055845. Sixth binomial transform is A153597.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000
• Index entries for linear recurrences with constant coefficients, signature (0,3).

Crossrefs

Cf. A000244 (powers of 3), A055845, A153597.

Programs

Magma

[ n le 2 select 5*n-4 else 3*Self(n-2): n in [1..35] ];

Mathematica

LinearRecurrence[{0,3},{1,6}, 50] (* G. C. Greubel, May 14 2016 *)

Formula

a(n) = (3+(-1)^n)*3^(1/4*(2*n-1+(-1)^n))/2.

G.f.: x*(1+6*x)/(1-3*x^2).