OFFSET
1,1
COMMENTS
Also, numbers k such that (k^3+1)/7 is a nonnegative integer. - Bruno Berselli, Jan 16 2016
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).
FORMULA
G.f.: x*(3+2*x+x^2+x^3)/((1+x+x^2)*(x-1)^2). - R. J. Mathar, Dec 04 2011
From Wesley Ivan Hurt, Jun 07 2016: (Start)
a(n) = a(n-1) + a(n-3) - a(n-4) for n>4.
a(n) = (21*n-9*cos(2*n*Pi/3)+sqrt(3)*sin(2*n*Pi/3))/9.
a(3k) = 7k-1, a(3k-1) = 7k-2, a(3k-2) = 7k-4. (End)
MAPLE
A047327:=n->(21*n-9*cos(2*n*Pi/3)+sqrt(3)*sin(2*n*Pi/3))/9: seq(A047327(n), n=1..100); # Wesley Ivan Hurt, Jun 07 2016
MATHEMATICA
Select[Range[0, 150], MemberQ[{3, 5, 6}, Mod[#, 7]] &] (* Wesley Ivan Hurt, Jun 07 2016 *)
PROG
(Magma) [n : n in [0..150] | n mod 7 in [3, 5, 6]]; // Wesley Ivan Hurt, Jun 07 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved