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Jan
10
comment Motivation for solution to constructing a set of 1983 distinct integers such that no three are consecutive terms of an arithmetic progression
Going just on the title (i.e. before I saw the limit to numbers less than 100.000) my immediate reaction was that powers of two would work, so there must be some constraint preventing them from being valid. That's another prompt to think of changing the base.
Jan
5
comment Cycle attack on RSA
If $p$ and $q$ are Sophie Germain safe primes, I think you can probably use Sylow's third theorem to prove that the probability of a random $e$ having order less than $\varphi(n)$ is $O(n^{-1/2})$. Proof left as an exercise for someone who knows more group theory than me.
Jan
5
comment One year course in Mathematics for Computer Science
The book Concrete Mathematics by Graham, Knuth and Patashnik came out of such a course at Stanford.
Jan
5
comment Cycle attack on RSA
The connection I was seeing is that in the smooth prime attack it describes a more sophisticated cycle attack and gives hints which allow you to estimate the probability of vulnerability.
Jan
4
comment Cycle attack on RSA
Does the accepted answer to crypto.stackexchange.com/questions/1151/… answer the question?
Jan
3
comment Does the math behind this joke work?
I think the joke could be tightened a bit to "Why do Hell's Angels never work from home? Because members of a cyclical group always commute."
Jan
2
comment Finding an appropriate axis of rotation for two points such that they can be rotated and translated to overlay a given line
@Steve, a curved plane? So when you say "lines" you actually mean "curves"?
Jan
2
comment Why is $\gcd(a,b)=\gcd(b,r)$ when $a = qb + r$?
But $a-b$ and $b$ don't have the same set of divisors. They have the same set of common divisors with $a$.
Dec
22
comment Proof that $\sum\limits_{i=1}^k \log(i)$ belongs to $O(k)$
Wikipedia has a different sum with a proof that it's $O(k)$.
Dec
18
comment Generalized Fibonacci sequences
@BrianM.Scott, thanks. That what I thought it should be, but it didn't fit.
Dec
18
comment Generalized Fibonacci sequences
What's the rule for constructing the table in the "first generalisation"?
Dec
15
comment How would I know if $f(x)=x^5-2x+10$ has a root at the interval $[-2, 2]$?
Intermediate value theorem, not mean value theorem, surely?
Dec
13
comment expected number of guesses in game of mastermind
Are you assuming perfect play?
Dec
9
comment How to go from Fermat’s little theorem to Euler’s theorem thought Ivory’s demonstration?
@gurghet, what? You don't need to do anything modulo the totient.
Dec
9
comment How to go from Fermat’s little theorem to Euler’s theorem thought Ivory’s demonstration?
@Ted, yes, if they're equal.
Dec
6
comment Counting barcodes
NB An alternative formulation is that you want to count the strings in the language $b\{b, w\}^{10}b$ which don't contain $bbb$ or $www$ as a substring.
Nov
23
comment In how many ways 3 flags of colors black, purple & yellow can be arranged at the corners of an equilateral triangle?
I can see a considerable number of possible interpretations of this question. For a start, it could be three distinguisable flags (one black, one purple, and one yellow) or three indistinguishable tricolour flags. Then there may or may not be an implied constraint that each corner has precisely one flag positioned at it. Finally the corners or the triangle may or may not be distinguishable.
Nov
23
comment In how many ways 3 flags of colors black, purple & yellow can be arranged at the corners of an equilateral triangle?
2! isn't 4. The answer is either 2 or 6 depending on what the question is (which isn't clear).
Nov
23
comment Is there a formal name for an equation that has no solution?
Surely the equation is insoluble, and to be inconsistent it would have to be a set of equations?
Nov
18
comment Where to find $\lambda$-calculus examples? For instance, how to check if a list is empty?
You don't have to expand from the inside out. Here you can just say $(\lambda l.l(\lambda a b.true)false)(\lambda fx.x)=_{\beta}(\lambda fx.x)(\lambda a b.true)false=_{\beta}false$