OFFSET
1,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).
FORMULA
G.f.: x*(1+2*x+3*x^2+x^3)/((1+x+x^2)*(x-1)^2). - R. J. Mathar, Oct 25 2011
From Wesley Ivan Hurt, Jun 10 2016: (Start)
a(n) = a(n-1) + a(n-3) - a(n-4) for n>4.
a(n) = (21*n-12+3*cos(2*n*Pi/3)+sqrt(3)*sin(2*n*Pi/3))/9.
a(3*k) = 7*k-1, a(3*k-1) = 7*k-4, a(3*k-2) = 7*k-6. (End)
a(n) = 2*n - 1 + floor(n/3). - Wesley Ivan Hurt, Dec 28 2016
MAPLE
A047282:=n->(21*n-12+3*cos(2*n*Pi/3)+sqrt(3)*sin(2*n*Pi/3))/9: seq(A047282(n), n=1..100); # Wesley Ivan Hurt, Jun 10 2016
MATHEMATICA
Select[Range[0, 150], MemberQ[{1, 3, 6}, Mod[#, 7]] &] (* Wesley Ivan Hurt, Jun 10 2016 *)
PROG
(Magma) [n : n in [0..150] | n mod 7 in [1, 3, 6]]; // Wesley Ivan Hurt, Jun 10 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved