## Prime One Less Than Square

#### Problem

It can be seen that $2^2 - 1 = 3$ is prime.

Find the next example of a prime which is one less than a perfect square.

Problem ID: 281 (15 Jul 2006) Difficulty: 2 Star

It can be seen that $2^2 - 1 = 3$ is prime.

Find the next example of a prime which is one less than a perfect square.

Problem ID: 281 (15 Jul 2006) Difficulty: 2 Star