Sum of all the numbers that can be formed using all the digits $2, 3, 3, 4, 4, 4$
102349
sum of all the numbers that can be formed using the digits 2,3,3,4,4,4..
103347
combinatorial proof of summation
42706
How many $N$ digits binary numbers can be formed where $0$ is not repeated
146746
A formula for the sum of the triangular numbers?
140433
The number of ways of writing an integer as a sum of two squares
90519
Combinatorial proof of $\sum\limits_{k=0}^n {n \choose k}3^k=4^n$
158004
A formula for $1^4+2^4+...+n^4$
7327
Sum of the digits of the number 2^1000
96585
Sums and permutation
147766
Sum of Permutations from 0 to n
113331
Number of ways a natural number can be written as sum of smaller natural number
853
Write down the sum of sum of  sum of digits of $4444^{4444}$
27001
How to calculate the following sum:
4559
How many ways can $133$ be written as sum of only $1s$ and $2s$
73570
Sum of (example: 0+1+2+3 = 6 , 0+1+2+3+4+5+6+7 = 28 and so on)
144779
The number of ways to represent $(n^2+n)/4$ as a sum of $n/2$ distinct integers in $1,\dots,n$
87626
Why are all $n$, s.t. the sum of digits of $n$ and $n^2$ coincide, $\equiv 0,1 \bmod 9$