A077847 Expansion of (1-x)^(-1)/(1-2*x-2*x^2+2*x^3).

1, 3, 9, 23, 59, 147, 367, 911, 2263, 5615, 13935, 34575, 85791, 212863, 528159, 1310463, 3251519, 8067647, 20017407, 49667071, 123233663, 305766655, 758666495, 1882398975, 4670597631, 11588660223, 28753717759, 71343560703, 177017236479, 439214158847

Offset: 0

Author

N. J. A. Sloane, Nov 17 2002

Keywords

• nonn
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (3, 0, -4, 2).

Crossrefs

Cf. A052987.

Programs

Mathematica

CoefficientList[Series[(1-x)^(-1)/(1-2x-2x^2+2x^3),{x,0,40}],x] (* or *) LinearRecurrence[{3,0,-4,2},{1,3,9,23},40] (* Harvey P. Dale, Apr 02 2013 *)

PARI

Vec((1-x)^(-1)/(1-2*x-2*x^2+2*x^3)+O(x^99)) \\ Charles R Greathouse IV, Sep 26 2012

Formula

a(n) = -1+2*A077937(n)-2*A077937(n-2). [From R. J. Mathar, Nov 10 2009]

a(0)=1, a(1)=3, a(2)=9, a(3)=23, a(n)=3*a(n-1)-4*a(n-3)+2*a(n-4). - Harvey P. Dale, Apr 02 2013