the problem is:

for n>=1,let an be the number of ways to write n as an ordered sum
of positive integers where each summand is at least 2.(For example, a5=3
because here we may represent 5 by 5,by 2+3, and by 3+2) Find and solve a
recurrence relation for an.

can someone kindly teach me how to solve this?i have been thinking on it for many hours...thanx