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Nov
3
comment How many possible color combinations?
I think the answer is 17952, let me check a few things.
Nov
2
comment Combinatorial prime problem
The smallest I found to need a power of 10 are: 799 = 2^10 - 3^2 * 5^2 and 851 = 3 * 5^4 - 2^10
Nov
2
comment Combinatorial prime problem
797 = 2^5 * 5*2 - 3
Nov
2
comment Prove $\left|\frac{z_1}{z_2}\right|=\frac{|z_1|}{|z_2|}$ for two complex numbers
Where did that square root come from? Can't you use that |z| = r when z = r(cosθ+isinθ)?
Nov
2
comment Proving two graphs are isomorphic in polynomial time - Bondy/Murty - Graph Theory Page 6
It works without a hitch because the graph has a lot of symmetries (self isomorphisms). I think you could identify any 5-cycle with any other (as a start) and it will work.
Oct
29
comment A geometric assembly: Triangle, circle, square, pentagon.
I think I've seen somewhere the second problem about the inverse and I vaguely remember the value 12 as limit.
Oct
24
comment $27 | (2x+1)^2 \implies 2x$ is a multiple of 9?
@RyanYu Then edit the title of your question.
Oct
3
comment Is this a isomorphism $(\mathbb Z,+) \to (Z,+)$ where $\varphi(n) = 2n$? Why not?
You are missing that there is no n such as φ(n)=1. Or φ(n)=3. So, the image of φ is not Z but a subset. You say " for every element in Z in the first group there is a element 2n in the second group." Right. But for every element y in Z in the second group is there is an element n in the first group such as φ(n)=y?
Oct
3
comment Solving $p_1^{e_1} p_2^{e_2}…p_k^{e_k}=e_1^{p_1} e_2^{p_2}…e_k^{p_k}$
@Tom-Tom I'm not sure but I see 4 or 5 adjacent related seqeunces, so I guess no. The "last modified" footer seems to in all OEIS sequences.
Oct
3
comment Solving $p_1^{e_1} p_2^{e_2}…p_k^{e_k}=e_1^{p_1} e_2^{p_2}…e_k^{p_k}$
@AnalysisIncarnate No, only just now searched for it. It doesn't have a date but several adjacent sequences were created by the same author (Olivier)
Oct
3
comment Solving $p_1^{e_1} p_2^{e_2}…p_k^{e_k}=e_1^{p_1} e_2^{p_2}…e_k^{p_k}$
@Tom-Tom and possible combinations of the above 3. (e.g. 2^4 * 3*3 * 5^7 * 7^5). Or what you said with "cycles of length 1 or 2" and the exception for 2^4.
Oct
3
comment Solving $p_1^{e_1} p_2^{e_2}…p_k^{e_k}=e_1^{p_1} e_2^{p_2}…e_k^{p_k}$
OEIS sequence A008478
Oct
3
comment Solving $p_1^{e_1} p_2^{e_2}…p_k^{e_k}=e_1^{p_1} e_2^{p_2}…e_k^{p_k}$
There's also 2^3 * 3^2. And (2^17 * 17^2) * (3^31 * 31^3), ...
Oct
3
comment Quick and painless definition of the set of real numbers
Continued fractions might be a good idea.
Aug
26
comment How many ways to generate unique multiplication result from given set?
There are 5 elevens, 5 sevens, 4 fives, 3 threes and 3 twos. And there are in total 5 distinct primes in the set. The (-N-1) calculation is needed because you don't include the "one factor" and the "zero factor" multiplications.
Aug
26
comment How many ways to generate unique multiplication result from given set?
If pi are the distinct prime numbers in the (multi)set and ni are the number of times the respective pi appears, then the result is Product(ni+1) - N - 1 (oh and N is the number of disticnt primes.) So for you last example would be (5+1)*(5+1)*(4+1)*(3+1)*(3+1) - 5 - 1 = 2874
Aug
26
comment How to show the convergence of this infinite series: $\frac{x}{1+x}- \frac{x^2}{1+x^2}+ \frac{x^3}{1+x^3}\dots$
@mike the question has: Given: 0<x<1
Jul
31
revised Are all fields vector spaces?
grammar corrections. Not sure about the phrasing of the last sentence, seems still wrong.
Jul
31
suggested approved edit on Are all fields vector spaces?
Apr
4
awarded  Excavator