P(notE)=1/2^2+1/3^2+1/5^2+...
-1/2^2*1/3^2-1/2^2*1/5^2-...
+1/2^2*1/3^2*1/5^2+....
-........
P(E)=1-P(notE),the limit, I quess ,is open question.