PUMaC 2015 Number Theory A Problem 5

Given that there are 24 primes between 3 and 100, inclusive, what is the number of ordered pairs (p, a) with p prime, 3 \leq p<100, and 1 \leq a<p such that the sum

a+a^{2}+a^{3}+\cdots+a^{(p-2)!}

is not divisible by p?