Question 53
Find the number of positive integers $x$ less than 100 for which
$$
3^{x}+5^{x}+7^{x}+11^{x}+13^{x}+17^{x}+19^{x}
$$
is prime.
$$
3^{x}+5^{x}+7^{x}+11^{x}+13^{x}+17^{x}+19^{x}
$$
is prime.
MathNet 2011 Question 53
Math Olympiad Vault · MathNet 2011