A174317 a(0)=1, a(1)=2, a(2)=1; for n>2, a(n) = 7*2^(n-3)-2.

1, 2, 1, 5, 12, 26, 54, 110, 222, 446, 894, 1790, 3582, 7166, 14334, 28670, 57342, 114686, 229374, 458750, 917502, 1835006, 3670014, 7340030, 14680062, 29360126, 58720254, 117440510, 234881022, 469762046, 939524094, 1879048190, 3758096382

Offset

0,2

Links

Table of n, a(n) for n=0..32.

Index entries for linear recurrences with constant coefficients, signature (3,-2).

Formula

G.f: (1+x-x^2+4*x^3-7*x^4)/(1-x)+(14*x^4)/(1-2*x).

a(n) = A026622(n-1), n>2. a(n) = A176448(n-3), n>2. - R. J. Mathar, Mar 01 2016

Example

a(4) = 14-2 = 12.
a(5) = 7*4-2 = 26.

Maple

taylor(1+2*z+z^2+5*z^3-((2*z^4)/(1-z))+((14*z^4)/(1-2*z)), z=0, 50);

Crossrefs

Cf. A174314, A174316

Sequence in context: A049950 A095216 A307258 * A144237 A350742 A268295

Adjacent sequences: A174314 A174315 A174316 * A174318 A174319 A174320

Keyword

nonn,easy

Author

Richard Choulet, Mar 15 2010

Extensions

Definition edited by Olivier Gérard, Oct 24 2012

Status

approved