Visualising the sum of the first $n$ positive odd integers
34338
Visually stunning math concepts which are easy to explain
20443
Calculate sum of squares of first $n$ odd numbers
114796
Direct proof that the product of odd integers is odd
65763
Number of ways to write n as a sum of k nonnegative integers
131080
Geometric representation of the sum of a Geometric Series
22154
Show that given a set of positive n integers, there exists a non-empty subset whose sum is divisible by n
32350
Compilation of proofs for the summation of natural squares and cubes
42831
How to derive the formula for the sum of the first $n$ odd numbers: $n^2=\sum_{k=1}^n(2k-1).$
52774
Computing an infinite sum using the Residue theorem
81729
Combinatorial proof of $\sum_{k=0}^{n}(-1)^{k}\binom{n}{k}(l-k)^n=n!$, using inclusion-exclusion
158124
Sum of all the positive integers problem
47148
Complete balanced (signed) residue System of an odd modulo m
68080
Evaluation of $\sum_{k=0}^n{n\choose k}^2u^k$
58264
How to derive the formula for the sum of the first $n$ perfect squares?
140172
How to compute the Riemann sum of $x^n$ for any positive integer $n$?
143271
Finite sum of reciprocal odd integers
45386
Fibonacci sequence emerging from integer partitioning