OFFSET
1,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).
FORMULA
a(n+1) = 3*n-2*floor(n/3)-(n^2 mod 3). - Gary Detlefs, Mar 19 2010
G.f.: x^2*(2+3*x+2*x^2)/((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>4.
a(n) = (21*n-21+3*cos(2*n*Pi/3)+sqrt(3)*sin(2*n*Pi/3))/9.
a(3k) = 7k-2, a(3k-1) = 7k-5, a(3k-2) = 7k-7. (End)
MAPLE
seq(3*n-2*floor(n/3)-(n^2 mod 3), n=0..52); # Gary Detlefs, Mar 19 2010
MATHEMATICA
Select[Range[0, 150], MemberQ[{0, 2, 5}, Mod[#, 7]] &] (* Wesley Ivan Hurt, Jun 09 2016 *)
PROG
(Magma) [n : n in [0..150] | n mod 7 in [0, 2, 5]]; // Wesley Ivan Hurt, Jun 09 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved