Discussion on: Challenge: Write the recursive Fibonacci algorithm in a different language.

Here's a Python variant for quite large numbers. Alas, due to recursion depth restrictions, any new calculated Fibonacci number should not have a larger sequence position than about 500 more than that of the highest already calculated.

def fib(a, F={}):
    if a in F:
        return F[a]
    if a < 2:
        return 1
    f = fib(a-1)
    F[a-1] = f
    return f + fib(a-2)

for i in range(0,50001,500):
    print("fib(%i) = %i"%(i,fib(i)))