Finding a closed formula for: $1\cdot2\cdot3+2\cdot3\cdot4+...+(n-2)\cdot(n-1)\cdot(n)$
124135
A general formula for $\sum (k-1)(k-2)(k-3)$?
122445
Sum of the series:$\frac{1}{1\cdot 2}+\frac{1\cdot3}{1\cdot2\cdot3\cdot4}+\cdots$
127150
Finding general formula of $\sum_{i=0}^n i^2 \binom{n}{i}$
116491
Closed form for $\sum_{k=0}^{m} {\binom {m}{k}} a^{k} (b+ck)^N$
29524
Formula for the sum $\sum_{i=2}^{n} \frac1{i^2-1}$
144772
Is there a recurrence relation which has no closed formula?
12423
"Closed" form for $\sum \frac{1}{n^n}$
23726
A closed form for $1^{2}-2^{2}+3^{2}-4^{2}+ \cdots + (-1)^{n-1}n^{2}$
61871
Formula for the $n$th term of $1, 2, 2, 3, 3, 3, 4, 4 ,4, 4, 5, ...$
114074
Intuitive/Visual proof that $(1+2+\cdots+n)^2=1^3+2^3+\cdots+n^3$
39659
Is there a closed formula for this summation?
3798
Finding formula for sum $S_n = \sum_{i=1}^n i(i-1)$
129801
Finding a closed form for $\sum^{n}_{k=1} \frac{k}{(k+1)!} $
14784
Inductive proof of the closed formula for the Fibonacci sequence
133420
Computing the binomial series: $\binom{n}{2}\cdot2^2+\binom{n}{4}\cdot2^4+\binom{n}{6}\cdot2^6+\cdots+ \binom{n}{n}\cdot2^n$
75367
Find a simple formula for $\binom{n}{0}\binom{n}{1}+\binom{n}{1}\binom{n}{2}+...+\binom{n}{n-1}\binom{n}{n}$
51864
$\left( \frac{1 \cdot 2}{p} \right) + \left( \frac{2 \cdot 3}{p} \right) + \cdots + \left( \frac{(p-2)(p-1)}{p} \right) = -1$