How do I derive the formula for the sum of squares?
16472
Sum of First $n$ Squares Equals $\frac{n(n+1)(2n+1)}{6}$
135914
Evaluate the sum of cubes
74471
Sum of numbers at vertex/face of cube
69194
Partitioning sum of squares
44577
Finding a formula to sum natural numbers up to $n$
89758
Is there a formula for $(1+i)^n+(1-i)^n$?
22840
The sum of the first $n$ squares is a square: a system of two Pell-type-equations
78632
Summation equation for $2^{x-1}$
41789
Fermat's theorem on sums of two squares
149685
Formula for $\sqrt{a-\sqrt{a+\sqrt{a+\ldots}}}$
98440
Show that any non-negative rational integer may be written as the sum of two squares if it is of the form....
67899
Integer squares of the form $x^4+x^3+x^2+x+1$
136582
Decomposing total sum of squares
29524
Formula for the sum $\sum_{i=2}^{n} \frac1{i^2-1}$
94060
Sum of square binomial coefficients
24222
Sum of the squares of the reciprocals of the fixed points of the tangent function
39909
Getting a closed form from $\sum_{i=1}^{n-1} \sum_{j=i+1}^{n} \sum_{k=1}^{j} 1$