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
G.f.: x*(3+x+x^2+2*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-6-12*cos(2*n*Pi/3)+4*sqrt(3)*sin(2*n*Pi/3))/9.
a(3k) = 7k-2, a(3k-1) = 7k-3, a(3k-2) = 7k-4. (End)
MAPLE
A047364:=n->(21*n-6-12*cos(2*n*Pi/3)+4*sqrt(3)*sin(2*n*Pi/3))/9: seq(A047364(n), n=1..100); # Wesley Ivan Hurt, Jun 08 2016
MATHEMATICA
LinearRecurrence[{1, 0, 1, -1}, {3, 4, 5, 10}, 60] (* Harvey P. Dale, Dec 03 2014 *)
Flatten[# + {3, 4, 5} & /@ (7 Range[0, 20])] (* or *)
Select[Range[0, 150], MemberQ[{3, 4, 5}, Mod[#, 7]] &] (* Robert G. Wilson v, Sep 26 2016 *)
PROG
(Magma) [n : n in [0..150] | n mod 7 in [3..5]]; // Wesley Ivan Hurt, Jun 08 2016
(PARI) a(n)=(n-1)\3*7 + (n-1)%3 + 3 \\ Charles R Greathouse IV, Sep 26 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved