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seen Feb 23 at 22:59

Feb
23
revised maximum nonattacking black and white queens on infinite chessboard
add example, clarify "nonattacking"
Feb
23
comment maximum nonattacking black and white queens on infinite chessboard
"Nonattacking" is a little misleading here: usually that means none of the queens can attack each other, but here it means that they can't attack the other color. I'll try to clarify that and add an example.
Feb
23
asked maximum nonattacking black and white queens on infinite chessboard
Feb
23
revised For what categories do category algebras exist?
add "convolution" term
Jan
3
comment Combinatorics: several problems
For (3), it's not clear what you're trying to count. I suspect this is just a lead-in to (4). For (4), I think we'll need to know how many of the two-feature symptoms are in list A and how many are in list B. In general, a single clear and specific problem would be more helpful.
Dec
29
answered When is negative square valid when checking a graph?
Dec
29
comment Combinatorics: several problems
Why are you trying to calculate these numbers?
Dec
29
revised Combinatorics: several problems
fixed part 1 answer
Dec
29
comment Combinatorics: several problems
Good point, I'll edit for that.
Dec
29
answered Combinatorics: several problems
Dec
29
comment Combinatorics: several problems
You might make a case for combining (1)-(4) in one question, although that's stretching it a bit, but I recommend a separate question for part (5).
Dec
27
comment What are the onto homomorphisms from the product ring $\prod_i \mathbb{Z}$?
Intriguing, @MartinBrandenburg. Where can I learn more about the infinite products? For example, how does one build an ideal from a filter as you mention above?
Dec
21
comment What are the onto homomorphisms from the product ring $\prod_i \mathbb{Z}$?
@Martin, actually I think I can! :-) But the answer is that I'm interested in both cases. Maybe someone would like to post an answer for the finite case.
Dec
19
answered Homomorphic image of a ring.
Dec
19
asked What are the onto homomorphisms from the product ring $\prod_i \mathbb{Z}$?
Dec
17
comment Geometric sequence, finding two variables
We'll need to know more about what you mean by $a$, $t_n$, and $S_n$.
Dec
17
comment For what categories do category algebras exist?
Is there a nice universal property satisfied by the definition of incidence algebras?
Dec
8
answered Assume $X$ and $Y$ be nonempty subsets of $R$ such that $x<y$ for every $x \in X$ and $y \in Y$. Prove that $\sup X \leq \inf Y$. Is my proof correct?
Dec
8
comment Smooth map from $S^1$ to $S^1$ with degree zero
@user114326: yes, there is. See my answer below.
Dec
8
answered Smooth map from $S^1$ to $S^1$ with degree zero