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38m
answered Sum of diminishing series with constant addition
56m
comment How does $n < 2^n$ become $\log n < n$ by taking log of both sides?
Also, sometimes (like in complexity analysis) multiplicative constants (like $\log 2$ here) are ignored.
1h
comment Is it possible to permute an unknown binary sequence so that two particular bits are equal?
In the original problem there is no overwrite, just an optional (depending on what the bits are) swap. In particular, the number of $1$ bits in the string is constant.
1h
comment Is it possible to permute an unknown binary sequence so that two particular bits are equal?
I think the answer is no for the original problem as well, but haven't figured out how to prove it.
1h
answered Is it possible to permute an unknown binary sequence so that two particular bits are equal?
1h
comment Is it possible to permute an unknown binary sequence so that two particular bits are equal?
The original problem is different from the one in the question. In the question, the bits always switch. In the original they only switch if $A=1, B=0$ I believe the answer to this question is no.
2h
revised How to find Bitwise AND of all numbers for a given range?
add info
2h
comment Why is x=1 not reflexive? (or determining the properties of reflexive relations)
@munchschair: no, for reflexive you just care about $(t,t)$. All pairs like that must be in the relation for the relation to be reflexive. Whether $(1,2)$ is in the relation is immaterial to whether the relation is reflexive-you can have all the extra pairs you want as long as you have the required ones.
2h
answered Find the greatest integer $N$ such that no two of its digits are equal and each digit is also its factor
2h
comment Find the greatest integer $N$ such that no two of its digits are equal and each digit is also its factor
Why can't $5$ appear? It would have to be the ones digit, but $15$ is an acceptable number. It is not the greatest. $0$ cannot be a digit at all.
3h
answered How to find Bitwise AND of all numbers for a given range?
3h
revised Neat Diophantine Equation Question
fix link
4h
answered linear programming problem - how much additional resources should I buy?
4h
comment Show that the Axioms are satisfied
For help on formatting math, you can see this
4h
revised Show that the Axioms are satisfied
improve formatting
4h
comment Show that the Axioms are satisfied
What have you tried? State the axioms and show that your set satisfies them. Where are you stuck?
5h
comment Show that the Axioms are satisfied
@ajotatxe: No, the denominator should be $2^n$. You can require that $a$ be odd if you like.
5h
comment Non-standard models for Peano Axioms
There is a discussion of this in The Incompleteness Phenomenon by Goldstern and Judah along with a sketch of what the model looks like if it is countable. It has a countable infinity of copies of $\Bbb Z$ of nonstandard numbers. The copies are ordered like $\Bbb Q$
13h
comment How to express a system of differential equations in a form suitable for numerical methods?
In Euler's method, you are doing $y_{n+1}=y_n+y'_n\Delta x$, so you need to supply a function $y'(x,y,stuff)$ and the method takes care of the rest. In the others it is the same, but they call $y'$ a number of times per step to reduce the errors (if the solution is smooth enough). If you are writing the integrator instead of using a library routine, it doesn't depend (too much) on the function you are integrating. Usually the suggestion is to test your routine on $y'=y$ first, as you know the solution.
14h
revised Closed form formula for $2^{2^1}+2^{2^2}+…+2^{2^n}$
added 3 characters in body