Find the sum of the reciprocals of all perfect squares whose prime factorization contains only 3, 5, and 7, i.e. $$\frac{1}{9}+\frac{1}{25}+\frac{1}{49}+\frac{1}{9}+\frac{1}{81}+\frac{1}{225}+\frac{1}{441}+\frac{1}{625}+\cdots$$