OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).
FORMULA
a(n) = a(n-1) + a(n-3) - a(n-4) for n>4.
a(n) = floor((8*n-6)/3). [Gary Detlefs, Mar 07 2010]
a(n) = 3*n-floor(n/3). [Gary Detlefs, Jul 09 2011]
G.f. x^2*(3+3*x+2*x^2) / ((1+x+x^2)*(x-1)^2). - R. J. Mathar, Oct 08 2011
From Wesley Ivan Hurt, Jun 13 2016: (Start)
a(n) = (24*n-21+3*cos(2*n*Pi/3)-sqrt(3)*sin(2*n*Pi/3))/9.
a(3k) = 8k-2, a(3k-1) = 8k-5, a(3k-2) = 8k-8. (End)
MAPLE
seq(floor((8*n-6)/3), n=1..52); # Gary Detlefs, Mar 07 2010
MATHEMATICA
f[n_] := 3 n - Floor[n/3]; Array[f, 52, 0] (* Or *)
Cases[ Range[0, 136], n_ /; MatchQ[ Mod[n, 8], 0 | 3 | 6]] (* Robert G. Wilson v, Jul 10 2011 *)
PROG
(Magma) [Floor((8*n-6)/3): n in [1..60]]; // Vincenzo Librandi, Jul 11 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved