SyntaxError

edit

You seem to be confusing symbolic variables with Python names. Since you plan to let a,b,n take som precise integer values, you should better define f = n^2+a*n+b only when a, b, n get a value, that is inside the loop.

I could help to rewrite the code, but I am not surre about your objective, do you want to find all tuples (a,b,n) in $\{1,40\} \times \{1,40\} \times \{0,40\}$ such that n^2+a*n+b is prime ?

Also, what are you trying to test when you write if f(n) in ZZ ?

EDIT

To test a couple (a,b), you can define the function:

def test(a, b):
    return all(is_prime(n^2+a*n+b) for n in range(1,41))

Now, you can run your test for the first pairs a,b:

for a in range(100):
    for b in range(100):
        if test(a,b):
            print(a,b)

Unfortunately, you will not find any pair in that range.

Note that when a,b,n are integers, n^2+a*n+b is also an integer.