Every number is the sum of three squares with signs
39135
Representation of integers by ternary quadratic form $x^2+y^2-z^2$
83862
How to prove that the number $1!+2!+3!+...+n!$ is never square?
58264
How to derive the formula for the sum of the first $n$ perfect squares?
158124
Sum of all the positive integers problem
60847
What three odd integers have a sum of 30?
377
Problem involving many squares and several variables.
91560
Square Fibonacci numbers
101708
Integers can be expressed as $a^3+b^3+c^3-3abc$
135458
When is a sum of consecutive squares equal to a square?
146746
A formula for the sum of the triangular numbers?
31485
Three negative and three positive $1$s in a serie
41789
Fermat's theorem on sums of two squares
125702
There is a square $Q$ consisting of $(0,0), (2,0), (0,2), (2,2)$
80671
Product of sums of square is a sum of squares.
16176
Primitive Pythagorean triple divisible by 3
9146
Proving that a list of perfect square numbers is complete
102349
sum of all the numbers that can be formed using the digits 2,3,3,4,4,4..