A number is called lucky if the sum of its digits, as well as the sum of the squares of its digits is a prime number. How many numbers between and inclusive, are lucky?

For example, and . Each number is tested below:

        digit   digit   squares
value   sum     squares sum 
20      2       4,0     4
21      3       4,1     5
22      4       4,4     8
23      5       4,9     13
24      6       4,16    20
25      7       4,25    29

We see that two numbers, , and are lucky.

Note: These lucky numbers are not to be confused with Lucky Numbers

Function Description

Complete the luckyNumbers function in the editor below. It should return an integer that represents the number of lucky numbers in the given range.

luckyNumbers has the following parameter(s):

• a: an integer, the lower range bound
• b: an integer, the higher range bound