The integer ```64``` is the first integer that has all of its digits even and furthermore, is a perfect square.
The second one is ```400``` and the third one ```484```.
Give the numbers of this sequence that are in the range ```[a,b] ```(both values inclusive)
Examples:
``` python
even_digit_squares(100, 1000) == [400, 484] # the output should be sorted.
even_digit_squares(1000, 4000) == []
``` 
Features of the random tests for ```even_digit_squares(a, b)```
```
number of Tests = 167
maximum value for a = 1e10
maximum value for b = 1e12
```
You do not have to check the entries, ```a``` and ```b``` always positive integers and ```a < b``` 
Happy coding!!
def is_even(x):
    return all(int(i) % 2 == 0 for i in str(x))
def even_digit_squares(a, b):
    first = int(a ** (1 / 2)) + 1
    last = int(b ** (1 / 2)) + 1
    return sorted([x * x for x in range(first, last) if is_even(x * x)])
def is_even(x):
    return all(int(i) % 2 == 0 for i in str(x))
def even_digit_squares(a, b):
    first = int(a ** (1 / 2)) + 1
    last = int(b ** (1 / 2)) + 1
    return sorted([x * x for x in range(first, last) if is_even(x * x)])