OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).
FORMULA
G.f.: (1-3*x^2-4*x^3)/((1-x)^2*(1+x+x^2)).
a(n) = A168072(n)/3^n.
From Wesley Ivan Hurt, Oct 05 2017: (Start)
a(n) = a(n-1) + a(n-3) - a(n-4) for n > 3.
a(n) = (45 - 48*n + 18*cos(2*(n-1)*Pi/3) - 9*cos(Pi*cos(2*(n-1)*Pi/3) + Pi*sin(2*(n-1)*Pi/3)/sqrt(3)) + 14*sqrt(3)*sin(2*(n-1)*Pi/3))/24. (End)
MATHEMATICA
LinearRecurrence[{1, 0, 1, -1}, {1, 1, -2, -5}, 50] (* G. C. Greubel, Jul 08 2016 *)
PROG
(PARI) Vec((1-3*x^2-4*x^3)/((1-x)^2*(1+x+x^2)) + O(x^70)) \\ Michel Marcus, Dec 03 2014
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Nov 18 2009
EXTENSIONS
Corrected by R. J. Mathar, Dec 03 2014
STATUS
approved