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Mar
30
asked Counter-example to exponential law for locally compact [non-Hausdorff] spaces
Jan
11
answered A three variable binomial coefficient identity
Jan
10
answered Combinatorial Identity
Jan
10
answered Finite summation with binomial coefficients, $\sum (-1)^k\binom{r}{k} \binom{k/2}{q}$
Jan
8
answered Is this morphism of spectra zero in the stable homotopy category?
Jan
3
answered Ramanujan-type trigonometric identities with cube roots, generalizing $\sqrt[3]{\cos(2\pi/7)}+\sqrt[3]{\cos(4\pi/7)}+\sqrt[3]{\cos(8\pi/7)}$
Dec
31
answered Proving $\sum_{k=0}^{2m}(-1)^k{\binom{2m}{k}}^3=(-1)^m\binom{2m}{m}\binom{3m}{m}$ (Dixon's identity)
Dec
31
answered Binomial Sum Related to Fibonacci: $\sum\binom{n-i}j\binom{n-j}i=F_{2n+1}$
Dec
30
answered Polynomial with a root modulo every prime but not in $\mathbb{Q}$.
Dec
30
answered How prove this $\prod_{1\le i<j\le n}\frac{a_{j}-a_{i}}{j-i}$ is integer
Dec
27
asked Combinatorial definition of Hall–Littlewood polynomials (sum over SSYT?)
Dec
26
answered Is there a “counting groups/committees” proof for the identity $\binom{\binom{n}{2}}{2}=3\binom{n+1}{4}$?
Dec
21
answered Evaluating Combination Sum $\sum{n+k\choose 2k} 2^{n-k}$
Dec
21
answered An example where $\frac{(2m)!(2n)!}{m!n!(m + n)!}$ is the number of ways of counting something?
Dec
20
answered Prove that for all non-negative integers $m,n$, $\frac{(2m)!(2n)!}{m!n!(m + n)!}$ is an integer.
Dec
20
answered What motiveted Gauss to formulate his theorem on quadratic reprocity?
Dec
13
asked Law of sines: uniform proof of Euclidean, spherical & hyperbolic cases
Jul
11
answered Recurrence $(n+2)\text{Cat}_{n+1}=(4n+2)\text{Cat}_n$ for non-crossing matchings
Jun
10
answered Example of something easier to count with $q$-analog?
May
26
answered Spin manifold and the second Stiefel-Whitney class