Sum of angles in a $3 \times 3$ grid
30600
Why does $\tan^{-1}(1)+\tan^{-1}(2)+\tan^{-1}(3)=\pi$?
18793
Partial sum of rows of Pascal's triangle
26790
Proving the geometric sum formula by induction
110975
Summation of reciprocals
70018
Sum of series (telescoping)
126424
The square of minimum area with three vertices on a parabola
138596
How to get all 24 rotations of a 3-dimensional array?
145690
Quadratic algorithm for 4-SUM
35864
Playing with numbers form $1$ to $n^2$ in an $n\times n$ grid
42270
Combinatorics - Painting the Unit Squares of a 3x3 Square
109180
Deriving Sum of a Geometric Progression
124373
Area of a parallelogram, vertices $(-1,-1), (4,1), (5,3), (10,5)$.
46606
Can an integer of the form $4n+3$ written as a sum of two squares?
140517
Sum of the entries in the matrix $A^3$
35629
Trisect a quadrilateral into a $9$-grid; the middle has $1/9$ the area
99335
Sum of all triangle numbers
79777
An olympiad Geometry problem involving triangles