sanity check--what am I doing wrong copying the fibonacci function?

I think this is exactly what Professor Guttag uses in Lecture 13: def fib(n): global numCalls numCalls += 1 print 'fib called with ', n if n <= 1: return 1 else: return fib(n-1) + fib(n-2) numCalls = 0 n = 6 res = fib(n) print 'fib of ', n,' = ',res, 'numCalls = ',res but when I run it, it gives me fib(6) = 13 What am I missing?

Nevermind. 13 is the answer he got in the lecture as well. I was just printing res instead of numCalls and that got me confused. Although, according to http://en.wikipedia.org/wiki/Fibonacci_number, fib(6) actually IS 8, which is what he 'corrects' early in the lecture.

Fib(n) is the sum of the previous two numbers in the series. It's traditional to start with 0,1 which makes fib(6)=8 (the series is 0,1,1,2,3,5,8). But, you can also start with 1,1 (which is easier to code; if n<=1 return 1), which makes fib(6)=13 (the series is 1,1,2,3,5,8,13).

Thanks!