last digit is a square and..... I've found some solutions for this questions but they were not impressive.
Question:
How many natural numbers are there in base $10$,whose last digit is perfect square,combination of last two digits is a perfect square,combination of last three digits is a perfect square,$\ldots$,combination of last $n$ digits is a perfect square?
For example $64$ is a number whose last digit is a perfect square and combination of last two digits is also a perfect square.
Kindly tell me how to approach this question.   

Answers are in the forms:-
(i)$4\times10^n$
(ii)$9\times10^n$
(iii)$10^n$
(iv)$49\times10^n$
(v)$64\times10^n$
(vi)$81\times10^n$
Where $n \in 0,2,4,6...$
