Any integer in 99, 999, 9999... sequence is not a perfect square
72761
Perfect square all 9's
44790
Find $n$ for which $\frac{n(n+1)}{2}$ is perfect square
112867
Find all digits $a,b$ such that the number $\overline{aabb}$ is a perfect square
122048
why is the set of all binary sequences not countable?
109305
Non-existence of natural numbers such that $\sqrt{n} +\sqrt{n+1} <\sqrt{x} +\sqrt{y} <\sqrt{4n+2}$
48430
Prove the following sequence always results in a perfect square.
76434
What is the measure of the set of numbers in $[0,1]$ whose decimal expansions do not contain $5$?
148803
501 distinct coprime integers between 1 and 1000?
143620
How many $n$-digit decimal sequences (using the digits $0 = 9$) are there in which the digits $1$, $2$ and $3$ all appear?
84220
Questions on perfect squares
90074
Show that the sequence $1,2,3,4,5,6,7,8,9,1,0,1,1,1,2,1,3,1,4,1,5,1,6,1,7,1,8,1,9,2,0,2,1,\cdots$ isn't periodic
21906
Show $3^m + 3^n +1$ cannot be a perfect square for $m,n$ being positive integers.
108919
Numbers till 400 divisible by 2, 3, 5, 7
112182
Sequence of positive integers such that their reciprocals are in arithmetic progression
116540
Positive integers less than 1000 without repeated digits
47109
Generate an integer that is not among four billion given ones
81822
How many integers between $1$ and $10^4$ contain exactly one $8$ and one $9$?