OFFSET
1,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).
FORMULA
G.f.: x*(1+x+3*x^2+2*x^3)/((1+x+x^2)*(x-1)^2). - R. J. Mathar, Dec 05 2011
From Wesley Ivan Hurt, Jun 09 2016: (Start)
a(n) = a(n-1) + a(n-3) - a(n-4) for n>1.
a(n) = 7*n/3-2+4*sin(2*n*Pi/3)/(3*sqrt(3)).
a(3k) = 7k-2, a(3k-1) = 7k-5, a(3k-2) = 7k-6. (End)
MAPLE
A047387:=n->7*n/3-2+4*sin(2*n*Pi/3)/(3*sqrt(3)): seq(A047387(n), n=1..100); # Wesley Ivan Hurt, Jun 09 2016
MATHEMATICA
Select[Range[200], MemberQ[{1, 2, 5}, Mod[#, 7]]&] (* or *) LinearRecurrence[ {1, 0, 1, -1}, {1, 2, 5, 8}, 90] (* Harvey P. Dale, Jun 05 2014 *)
PROG
(Magma) [n : n in [0..150] | n mod 7 in [1, 2, 5]]; // Wesley Ivan Hurt, Jun 09 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved