Proofs: n is pos. integer; prove or disprove n=p+a^2, with

[joyful_jester]

n is a positive integer and I have to prove or disprove that n=p+a^2, where 'a' is an integer and p is prime or 1. I have no idea how to start so maybe if I got a starting point I could finish? I know n > 0 but every theorum I have includes another integer or n>1. Any help would be great.