A prime power is a prime or positive integer power of a prime. A test for a number being a prime is implemented in the Wolfram
Language as PrimePowerQ[n].
The first few prime powers are 2, 3, 4, 5, 7, 8, 9, 11, 13, 16, 17, 19, 23, 25, ... (OEIS A000961). The first few prime powers
with power
are given by 4, 8, 9, 16, 25, 27, 32, 49, 64, 81, ... (OEIS A025475).
The number of prime powers (exponents ) up to is given by