Can all positive integers of the form $4n+1$ be expressed as the sum of two squares?
92106
Prove that $n$ is a sum of two squares?
105564
If $n$ is a positive integer greater than 1 such that $3n+1$ is perfect square, then show that $n+1$ is the sum of three perfect squares.
144779
The number of ways to represent $(n^2+n)/4$ as a sum of $n/2$ distinct integers in $1,\dots,n$
140433
The number of ways of writing an integer as a sum of two squares
142580
Prove that a perfect square is either a multiple of $4$ or of the form $4q+1$.
132125
finding if two binary quadratic forms represent the same integers
146241
If $a \in \Bbb Z$ is the sum of two squares then $a$ can't be written in which of the following forms?
110441
Closed form for a formula with a summation over $i\binom{n-i}{k-1}$, and combinatorial proof?
158004
A formula for $1^4+2^4+...+n^4$
98443
Find positive integers such that $2n^3 + 5|n^4 +n+1$
59782
Are there any $n$ for which $ n^4+n^3+n^2+n+1$ is a perfect square?
153769
Numbers that can be expressed as the sum of two cubes in exactly two different ways
131625
Expressing an integer as the sum of three squares
56985
Show that every positive integer has a unique representation in the form $50k+l$...?
19588
$n!+1$ being a perfect square
129755
Weighted sum of squares, in a finite field
106716
The sum of square roots of non-perfect squares is never integer