OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..3000
Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).
FORMULA
a(n+1) = 7*floor(n/3)+(n mod 3)+2. - Gary Detlefs, Mar 09 2010
G.f.: x*(2+x+x^2+3*x^3)/((1+x+x^2)*(x-1)^2). - R. J. Mathar, Dec 04 2011
From Wesley Ivan Hurt, Jun 08 2016: (Start)
a(n) = a(n-1) + a(n-3) - a(n-4) for n>4.
a(n) = (21*n-15-12*cos(2*n*Pi/3)+4*sqrt(3)*sin(2*n*Pi/3))/9.
a(3k) = 7k-3, a(3k-1) = 7k-4, a(3k-2) = 7k-5. (End)
MAPLE
seq(7*floor(n/3)+(n mod 3)+2, n= 0..52); # Gary Detlefs, Mar 09 2010
MATHEMATICA
Select[Range[0, 150], MemberQ[{2, 3, 4}, Mod[#, 7]] &] (* Wesley Ivan Hurt, Jun 08 2016 *)
PROG
(Magma) [n : n in [0..150] | n mod 7 in [2..4]]; // Wesley Ivan Hurt, Jun 08 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved