A166027 a(n) = 6*a(n-2) for n > 2; a(1) = 4, a(2) = 1.

4, 1, 24, 6, 144, 36, 864, 216, 5184, 1296, 31104, 7776, 186624, 46656, 1119744, 279936, 6718464, 1679616, 40310784, 10077696, 241864704, 60466176, 1451188224, 362797056, 8707129344, 2176782336, 52242776064, 13060694016, 313456656384

Offset: 1

Author

Klaus Brockhaus, Oct 04 2009

Keywords

• nonn
• easy

Comments

Interleaving of 4*A000400 and A000400.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..300
• Index entries for linear recurrences with constant coefficients, signature (0, 6).

Crossrefs

Cf. A000400 (powers of 6), A166023.

Programs

Magma

[ n le 2 select 7-3*n else 6*Self(n-2): n in [1..29] ];

Mathematica

Join[{4, 1, 24}, LinearRecurrence[{0, 6}, {6, 144}, 25]] (* G. C. Greubel, Apr 21 2016 *)

Formula

a(n) = 6^(1/4*(2*n+3+(-1)^n))*(25-23*(-1)^n)/72.

G.f.: x*(4+x)/(1-6*x^2).