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1h
answered Sum of super exponentiation
3h
comment What's a group whose group of automorphisms is non-abelian?
Of course the real question was not to name such a group, but to describe how to find such a group. I find it natural to try the simplest example of a nonabelian group ($S_3$) and try to ensure that $S_3$ is a subgroup ioof the automorphism group. As permuting things is the favorite pastime of $S_3$, something like above might jump to your mind.
3h
answered What's a group whose group of automorphisms is non-abelian?
3h
answered Jimmy got a 38.5% (± 0.05%) on his math test. How many questions did the test have at a minimum?
4h
comment If I flip a coin 1000 times in a row and it lands on heads all 1000 times, what is the probability that it's an unfair coin?
The Finland 1 penni of 1969 weighs just 0.45g :) -- But I guess there are only about $10^{15}$ coins in the world (this discussion ends up with about $2\cdot 10^{12}$ coins in the US).
8h
answered Proof the series is finite using following inequality
8h
revised Proof the series is finite using following inequality
added 126 characters in body
8h
comment Show that the sum of (outdeg(v)-indeg(v))=0
Or note that $$\sum_{v\in V}(\operatorname{outdeg}(v)-\operatorname{indeg}(v))=\sum_{v\in V}(\sum_{w,vw\in E}1-\sum_{w,wv\in E}1)=\sum_{vw\in E}1-\sum_{wv\in E}1=0 $$
10h
comment Sum of super exponentiation
It is unlikely that the period is much smaller. Try dynamic programming
10h
answered Is my example of non equivalent maps correct?
21h
answered limit and infinite ordinals: same thing?
23h
comment Issue with associativity of group
@MattSamuel Virtually all weird group operations on (subsets of) $\mathbb R$ that are posed as exercise can be solved by exhibiting an isomorphism such as here - but often it is easier to guess. With this in mind, and assuming a Möbius transform as $f$, I noted that subtract one, take reciprocals, subtract one would at least map the interval to the positive reals, i.e., a set that we recognize as a standard group. And - surprise, surpirise - the bijection turns out to be an isomorphism ...
23h
comment In what structures does $ (-1)^2 = 1$?
@Gil-Mor Repeat: Not groups
1d
answered Prove $\exists$ $v \in V$ so that $(v , f(v))$ is a basis of $V$
1d
answered Power set of $\{\emptyset,\{\emptyset\}\}$
1d
answered Issue with associativity of group
1d
answered Does meet of two partitions of a set always exist?
1d
comment How can you confirm that a problem is open?
Add a "citation needed" to the Wikipedia article and wait ;)
1d
comment G acts freely on X. G is paradoxical implies X is also paradoxical
$\phi$ is bijective
1d
comment Polygons - necessity of checking for collinearity with edge incident to diagonal's vertices?
$v_{i+2}$ could be between $v_i$ and $v_{i+3}$