A163888 a(n) = 2*a(n-2) for n > 2; a(1) = 5, a(2) = 4.

5, 4, 10, 8, 20, 16, 40, 32, 80, 64, 160, 128, 320, 256, 640, 512, 1280, 1024, 2560, 2048, 5120, 4096, 10240, 8192, 20480, 16384, 40960, 32768, 81920, 65536, 163840, 131072, 327680, 262144, 655360, 524288, 1310720, 1048576, 2621440, 2097152, 5242880

Offset

1,1

Comments

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

Binomial transform is A163607, second binomial transform is A163608, third binomial transform is A163609, fourth binomial transform is A163610, fifth binomial transform is A163611.

Links

G. C. Greubel, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (0, 2).

Formula

a(n) = (7 - 3*(-1)^n)*2^((2*n-5+(-1)^n)/4).

G.f.: x*(5+4*x)/(1-2*x^2).

Mathematica

Transpose[NestList[{Last[#], 2First[#]}&, {5, 4}, 40]] [[1]]  (* Harvey P. Dale, Mar 14 2011 *)
LinearRecurrence[{0, 2}, {5, 4}, 41] (* Ray Chandler, Aug 14 2015 *)

Prog

(Magma) [ n le 2 select 6-n else 2*Self(n-2): n in [1..41] ];
(PARI) x='x+O('x^50); vec(x*(5+4*x)/(1-2*x^2)) \\ G. C. Greubel, Aug 07 2017

Crossrefs

Cf. A020714 (5*2^n), A000079 (powers of 2), A163607, A163608, A163609, A163610, A163611.

Sequence in context: A286461 A152064 A088482 * A363323 A309545 A285105

Adjacent sequences: A163885 A163886 A163887 * A163889 A163890 A163891

Keyword

nonn

Author

Klaus Brockhaus, Aug 06 2009

Status

approved