How do I partition a given number N as a sum of all prime numbers below it?

for ex: 8 can be partitioned as 2+2+2+2(2 is prime) or 3+2+3(3 and 2 is prime) or 5+3(5 and 3 are prime).

for ex: 8 can be partitioned as 2+2+2+2(2 is prime) or 3+2+3(3 and 2 is prime) or 5+3(5 and 3 are prime).