A164682 a(n) = 2*a(n-2) for n > 2; a(1) = 5, a(2) = 8.

5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640, 1024, 1280, 2048, 2560, 4096, 5120, 8192, 10240, 16384, 20480, 32768, 40960, 65536, 81920, 131072, 163840, 262144, 327680, 524288, 655360, 1048576, 1310720, 2097152, 2621440, 4194304

Offset: 1

Author

Klaus Brockhaus, Aug 21 2009

Keywords

• nonn
• easy

Comments

Interleaving of A020714 and A000079 without initial terms 1, 2, 4.

First differences are in A162255.

Binomial transform is A135532 without initial terms -1, 3. Fourth binomial transform is A164537.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000
• Index entries for linear recurrences with constant coefficients, signature (0, 2).

Crossrefs

Equals A094958 (numbers of the form 2^n or 5*2^n) without initial terms 1, 2, 4.

Cf. A020714 (5*2^n), A000079 (powers of 2), A162255, A135532, A164537.

Programs

Magma

[ n le 2 select 2+3*n else 2*Self(n-2): n in [1..40] ];

Mathematica

LinearRecurrence[{0,2},{5,8},60] (* Harvey P. Dale, Jul 20 2022 *)

Formula

a(n) = (9-(-1)^n)*2^(1/4*(2*n-5+(-1)^n)).

G.f.: x*(5+8*x)/(1-2*x^2).