well, if you know that every number greater than or equal to 2 can be expressed as a product of prime numbers... and 3 is a prime number... and 2^n is a product of n 2's... there you go.
well, if you know that every number greater than or equal to 2 can be expressed as a product of prime numbers... and 3 is a prime number... and 2^n is a product of n 2's... there you go.