${2^k-1\choose a}$ is odd?
13525
Prove: If $n=2^k-1$, then $\binom{n}{i}$ is odd for $0\leq i\leq n$
4991
Proving by induction that $ \sum_{k=0}^n{n \choose k} = 2^n$
136037
${n\choose 2} - {k\choose 2} = {n-k\choose 2} +k(n-k)$ Marked box or unmarked box
18633
Prove every odd integer is the difference of two squares
44484
Combinatorial identity $i{n \choose i } =n {n-1 \choose i - 1}$
63774
If a and b are odd integers, then $8\mid (a^2-b^2)$
86168
Is $2^k = 2013...$ for some $k$?
47720
Isomorphism from Natural numbers to the Odd Natural numbers
94326
a square in a finite field of odd order
143132
How to reverse the $n$ choose $k$ formula?
101573
Subtracting even and odd binomial coefficients?
3786
Help finding a combinatorial proof of $k {n \choose k } = n {n - 1 \choose k -1}\;$
147428
Probability of picking an odd number from the set of naturals?
41700
Are Mersenne prime exponents always odd?
120498
Why perfect square has odd number of factors
28957
Verifying that $2^{44}-1$ is divisible by $89$
68824
Show that $\frac{(3^{77}-1)}{2}$ is odd and composite