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May
14
comment Expected number of returns by time n in a symmetric 1-d random walk?
possible duplicate of Expected number of returns to zero in a symmetric random walk - closed form
May
13
comment Proving that $SL_2(\mathbb{Z}_5) / \{\pm I\}\simeq A_5$
cf. math.stackexchange.com/q/93762/152
May
6
comment Combinatorial definition of Hall–Littlewood polynomials (sum over SSYT?)
...but extracting something explicit for HL polynomials from that doesn't look like an easy task...
May
6
comment Combinatorial definition of Hall–Littlewood polynomials (sum over SSYT?)
Wikipedia page on Macdonald polynomials a) doesn't contain words 'semi-standard' or 'augmented'; b) doesn't give a combinatorial description of Macdonald polynomials — it mentions a description of transformed Macdonald polynomials that uses 'certain combinatorial statistics' inv and maj. I guess details can be found in arxiv.org/abs/math/0409538
Apr
10
comment A reference for a combinatorial identity
The second form looks like just a Vandermonde's identity ($\binom{i+k-1}i=\pm\binom{-k}i$ etc).
Apr
8
comment Stiefel-Whitney classes with Z-coefficients
(Re: The only problem I see is with the Steenrod square operation which may be undefined for integral coefficients) Well, yes there are no non-trivial stable operations from H(-;Q) to H(-;Q), after all...
Apr
7
reviewed Close Simplifying $\arctan\left(\frac{1}{\tan \alpha}\right)$
Apr
6
reviewed Leave Open Every prime is maximal in a Jacobson ring?
Apr
6
reviewed Close $\frac{1}{2}!$ aka $\Gamma(\frac{3}{2})$
Apr
5
reviewed Close Find $\lim_{x\to 0} \frac{\sin\left((2t+1)x\right)}{(t+1)x}$
Apr
5
reviewed Close finding all singularities of $f(z)= (z \sin z ) / (1-\cos z)$
Apr
5
reviewed Close Can modulo(remainder) be distribute over division?
Apr
5
reviewed Leave Open Evaluating $ \sum_{n=1}^\infty \frac{1}{n^2 2^n} $
Apr
5
reviewed Close Prove that $1+20^1+20^2+\cdots+20^{21}\equiv 0\pmod{23}$
Apr
5
reviewed Close Floor and Ceiling Proofs
Apr
5
reviewed Leave Closed Projection of a Jinc is a Sinc
Apr
5
reviewed Leave Open Proving real polynomials of degree greater than or equal to 3 are reducible
Apr
5
reviewed Leave Open Examples of functors that preserves products but not equalizers, and vice versa.
Apr
5
reviewed Close How to show that an object is a discrete valuation ring? (Fulton, Exercise 2.14)
Apr
5
reviewed Close What is $2^{7!}\bmod{2987}$