OFFSET
0,3
COMMENTS
Also, numbers congruent to {0,1,4,6} mod 9.
LINKS
Clark Kimberling, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,0,0,1,-1).
FORMULA
a(n) = (18*n - 5 + 3*(-1)^n + (1 - i)*(-i)^n + (1 + i)*i^n)/8, where i = sqrt(-1).
a(n) = a(n-1) + a(n-4) - a(n-5).
G.f.: (x*(1 + 3*x + 2*x^2 + 3*x^3))/(1 - x - x^4 + x^5).
MATHEMATICA
f[n_]:=Floor[(3/2)Floor[3n/2]];
t=Table[f[n], {n, 0, 70}]
LinearRecurrence[{1, 0, 0, 1, -1}, {0, 1, 4, 6, 9}, 60] (* Harvey P. Dale, Jun 21 2021 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jul 20 2012
STATUS
approved