Fortunate number

A Fortunate number is a concept from number theory that refers to a positive integer \( n \) such that \( n + 1 \) is either a prime number or is a prime power (a number of the form \( p^k \) where \( p \) is a prime and \( k \) is a positive integer). Essentially, the Fortunate numbers are obtained by adding 1 to the numbers in the sequence of primes or prime powers.