A166249 a(n) = 2*a(n-1) - a(n-3) + 2*a(n-4) for n>3, a(0)=a(1)=1, a(2)=0, a(3)=2.

1, 1, 0, 2, 5, 12, 22, 43, 84, 170, 341, 684, 1366, 2731, 5460, 10922, 21845, 43692, 87382, 174763, 349524, 699050, 1398101, 2796204, 5592406, 11184811, 22369620, 44739242, 89478485, 178956972, 357913942, 715827883, 1431655764, 2863311530

Offset: 0

Author

Paul Curtz, Oct 10 2009

Keywords

• nonn
• easy

Links

• G. C. Greubel, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (2,0,-1,2).

Programs

Mathematica

LinearRecurrence[{2, 0, -1, 2}, {1, 1, 0, 2}, 100] (* G. C. Greubel, May 08 2016 *)

Formula

From R. J. Mathar, Nov 09 2009: (Start)

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

a(n) = A001045(n) + A010892(n+1). (End)

Extensions

Edited by N. J. A. Sloane, Oct 13 2009

Extended by R. J. Mathar, Nov 09 2009