This reiterative formula is a repeating formula with some similar results as follows:
f(11) = 11 f(26) = 11
f(14) = .8333 f(29) = .8333
f(17) = -.0909 f(32) = -.0909
f(20) = -1.2 f(35) = -1.2
f(23) = 11 f(38) = 11 and so on repeating on a n = 12 repeat interval
Counting out to f(2003) it is on the f(11) interval, so f(2003) = 11