Lucas numbers
I think I have an idea.
It appears that we have: L^m(i) = V_{2^m}(1,-1), where i is the square root of -1, m is greater than 1, and V_n(1,-1) is a Lucas number defined by: V_0=2 , V_1=1, V_{n+1}=V_n+V_{n-1}. Look at "The Little Book of BIGGER primes" by Paulo Ribenboim, 2nd...