a(1)=1/2,
a(2) = 1 - 1/a(1) = -1,
a(3) = 1 - 1/a(2) = 2,
a(4) = 1 - 1/a(3) = 1/2 = a(1),
a(5) = 1 - 1/a(4) = 1 - 1/a(1) = a(2),
a(6) = a(3),
...
a(3n-2) = a(1) = 1/2,
a(3n-1) = a(2) = -1,
a(3n) = a(3) = 2,
a(16) = a(3*6-2) = a(1) = 1/2