OFFSET
1,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).
FORMULA
G.f.: x*(1+x+x^2+5*x^3)/((1-x)^2*(1+x+x^2)). [Colin Barker, May 13 2012]
a(n) = 1+8*floor((n-1)/3)+((n-1) mod 3). - Alois P. Heinz, May 13 2012
From Wesley Ivan Hurt, Jun 10 2016: (Start)
a(n) = a(n-1) + a(n-3) - a(n-4) for n>4.
a(n) = (24*n-30-15*cos(2*n*Pi/3)+5*sqrt(3)*sin(2*n*Pi/3))/9.
a(3k) = 8k-5, a(3k-1) = 8k-6, a(3k-2) = 8k-7. (End)
MAPLE
A047475:=n->(24*n-30-15*cos(2*n*Pi/3)+5*sqrt(3)*sin(2*n*Pi/3))/9: seq(A047475(n), n=1..100); # Wesley Ivan Hurt, Jun 10 2016
MATHEMATICA
Flatten[#+{1, 2, 3}&/@(8*Range[0, 20])] (* or *) LinearRecurrence[{1, 0, 1, -1}, {1, 2, 3, 9}, 70] (* Harvey P. Dale, Nov 06 2013 *)
PROG
(Magma) [n : n in [0..150] | n mod 8 in [1..3]]; // Wesley Ivan Hurt, Jun 10 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved