A positive integer is called a perfect\:power if it can be written in the form a^b, where a and b are positive integers with b\ge2. For example, 32 and 125 are perfect powers because 32=2^5 and 125=5^3. The increasing sequence2,3,5,6,7,10,\dots

consists of all positive integers which are not perfect powers. The sum of the squares of the digits of the 1000th number in this sequence is

**Answer Choices**

A. 42

B. 26

C. 33

D. 18

E. 21