Formula for combinatorial series sum
8806
Summation of binomial coefficients
57549
Finding the sum $\sum_{k=1}^rk^2\binom {n-k}{r-k}$
112036
sum of series $\frac{n}{1\cdot 2 \cdot 3}+\frac{n-1}{2\cdot 3\cdot 4}+\frac{n-2}{3\cdot 4 \cdot 5}+\cdots \cdots n$ terms
142978
combinatorics: sum of product of integer compositions
7302
$\sum k! = 1! +2! +3! + \cdots + n!$ ,is there a generic formula for this?
19571
Combinatorial proof for $\sum_{k = 0}^n \binom {r+k} k = \binom {r + n + 1} n$
125148
Summation of series $\sum_{k=0}^\infty 2^k/\binom{2k+1}{k}$
124135
A general formula for $\sum (k-1)(k-2)(k-3)$?
151085
Simplify the sum $ \sum_{i=0}^{k}(-1)^i i \binom{n}{i} \binom{n}{k-i}$
38741
Finding a general formula for summation
626
Sum of combinations with varying $n$
146746
A formula for the sum of the triangular numbers?
60860
Combinatorial proof of $\sum_{i = 0}^{n} \binom{i}{r - 1} = \binom{n + 1}{r}$ and then use result to find a formula for $1^2 + 2^2 + \ldots + n^2$
8905
Sum the series $\frac{3}{1⋅2⋅4}+\frac{4}{2⋅3⋅5}+ \frac{5}{3⋅4⋅6}+...\text{(upto n terms)}$
83229
Nested summations and their relation to binomial coefficients
131080
Geometric representation of the sum of a Geometric Series
31721
Series with specific notation