On splitting a number as the sum of two squares.
50128
Efficiently finding two squares which sum to a prime
134765
Is an integer a sum of two rational squares iff it is a sum of two integer squares?
154082
Product of factorials divided by factorial to produce perfect square
40080
Sum of multiples of $2$ coprime numbers cover positive integers
7073
How to get to the formula for the sum of squares of first n numbers?
9118
Polynomial division: an obvious trick? [reducing mod $\textit{simpler}$ multiples]
22840
The sum of the first $n$ squares is a square: a system of two Pell-type-equations
26607
The idea behind the sum of powers of 2
43864
Splitting very big numbers over several lines
103347
combinatorial proof of summation
101835
Which rationals can be written as the sum of two rational squares?
115686
A finite summation of double binomial coefficients
41789
Fermat's theorem on sums of two squares
92106
Prove that $n$ is a sum of two squares?
47060
Split $n$ into nontrivial factors via a nontrivial square-root of $1\!\pmod{\!n}$
32350
Compilation of proofs for the summation of natural squares and cubes
38018
Arrangement of integers in a row such that the sum of every two adjacent numbers is a perfect square.