closed form for $\binom{n}{0}+\binom{n}{3}+\binom{n}{6}+...+\binom{n}{n}$
108275
How do I count the subsets of a set whose number of elements is divisible by 3? 4?
17638
Sum with binomial coefficients: $\sum_{k=0}^{n}{2n\choose 2k}$
146762
Closed form for $\sum_{k=0}^{n} \binom{n}{k}\frac{(-1)^k}{(k+1)^2}$
70248
Closed-form expression for $\sum_{k=0}^n\binom{n}kk^p$ for integers $n,\,p$
50226
Prove the identity $\sum_{k=0}^{n}\sum_{r=0}^{k} \binom{k}{r} \binom{n}{k} = 3^n$
75367
Find a simple formula for $\binom{n}{0}\binom{n}{1}+\binom{n}{1}\binom{n}{2}+...+\binom{n}{n-1}\binom{n}{n}$
634
Closed form formula for $\sum\limits_{k=1}^n k^k$
49741
Finding a closed form for a recurrence relation $a_n=3a_{n-1}+4a_{n-2}$
87589
Evaluate $\binom{n}{0}+\binom{n}{2}+\binom{n}{4}+...+\binom{n}{2k}$
112827
Find the sum of the binomial coefficients
72639
Show that $\sum_{k=0}^n\binom{3n}{3k}=\frac{8^n+2(-1)^n}{3}$
127150
Finding general formula of $\sum_{i=0}^n i^2 \binom{n}{i}$
42736
Is there a closed form for $\sum_{k=0}^n \frac{x^k}{k!}$?
12423
"Closed" form for $\sum \frac{1}{n^n}$
14239
How to show $\sum_{k=0}^{n}\binom{n+k}{k}\frac{1}{2^k}=2^{n}$
106008
Combinatorial Identity $(n-r) \binom{n+r-1}{r} \binom{n}{r} = n \binom{n+r-1}{2r} \binom{2r}{r}$
108401
Sum of binomial coefficients $\sum_{k=0}^{n}(-1)^k\binom{n}{k}\binom{2n - 2k}{n - 1} = 0$