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2d
answered System of linear equations: and a small perturbation
2d
comment Counting Coprime Numbers in a range:
Rather than bothering to factor $n$, if $b - a$ is small enough to do that you might as well just compute $\gcd(n,x)$ for each $x$ in the interval.
2d
comment Counting Coprime Numbers in a range:
The inclusion-exclusion method for the number coprime to $n$ in $[1,k]$ gives you $$T(n,k) = \sum_{d \mid n} \mu(d) \lfloor k/d \rfloor $$ which is OEIS sequence A078401 (for $k \le n$).
2d
comment Sum of $n$ numbers dividable by $n$ from $(n-1)^2-1$ numbers.
You don't understand "Suppose it was not true"?
2d
comment Are the any **non-trivial** functions where $f(x)=f'(x)$ not of the form $Ae^x$
Almost everywhere in the sense of Lebesgue measure. en.wikipedia.org/wiki/Almost_everywhere
2d
answered Find an example of a sequence not in $l^1$ satisfying certain boundedness conditions.
2d
comment Integral tending to an integral for $\pi$
When you write $\int_0^1 (1 - a x)^{1/2}\; dx$, you are implicitly stating that $a$ is not a function of $x$. If you want it to be a function of $x$, you should write $\int_0^1 (1-a(x) x)^{1/2}\; dx$. Of course with $a(x)$, you can't use the same integration method that you could with $a$ being constant.
2d
answered Constructing a Fractional Linear Map
2d
comment Are the any **non-trivial** functions where $f(x)=f'(x)$ not of the form $Ae^x$
@Ryan a function that is not everywhere differentiable can hardly satisfy an equation involving its derivative. But in fact any absolutely continuous function $f$ that satisfies $f' = f$ almost everywhere is of the form $A e^x$.
2d
answered How to find inverse of generator of a finite field?
2d
answered The constant of integration in the solution to the differential equation $-4 g(x)=2 x g'(x)$
2d
revised Sum of $n$ numbers dividable by $n$ from $(n-1)^2-1$ numbers.
added 28 characters in body
2d
answered Sum of $n$ numbers dividable by $n$ from $(n-1)^2-1$ numbers.
2d
answered Function poles and divergence of series
2d
answered Closed form formula for discrete sums
May
20
answered Hermitian operator and numerical range
May
19
answered Prove that there are infinitely many composite numbers n so that…
May
19
comment Prove that there are infinitely many composite numbers n so that…
The sequence is oeis.org/A073631. No proof of infiniteness there, though,
May
19
comment Prove that there are infinitely many composite numbers n so that…
Your claim about $p^t$ is not true. Try $n = 23^2$.
May
19
comment Cardinality of a set of permutations of integers mod $p$.
Good advice, @bburGsamohT . It leads to < oeis.org/A004204 >, and I suspect the Graham and Lehmer reference there may be useful.