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Jan
21
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Dec
16
comment How Symmetric is Diophantine Approximation using Fractions with Square Denominators?
These can't be all of the best approximations, because they are all less than the Liouville number.
Dec
14
comment A question regarding a fragment of Robinson Arithmetic
In your language you can say that every element is even or odd. This is true in the non-negative integers under addition but false for the set of polynomials with non-negative leading coefficients (under addition, with successor defined in the obvious way.)
May
18
awarded  Nice Question
Apr
6
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Apr
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revised divisible by all standard prime numbers
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Apr
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revised divisible by all standard prime numbers
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Apr
2
answered divisible by all standard prime numbers
Jan
22
awarded  Enlightened
Jan
22
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Sep
10
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Aug
27
comment Algorithm for determining when polynomial iteration is bounded?
@Per: Thank you for the reference to the result on IFS undecidability. Alas, I don't see how to the IFS result here. However the second point, about the map $x\to x-1/x$ seems really interesting. Do you have a reference?
Aug
26
asked Algorithm for determining when polynomial iteration is bounded?
Jul
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Jun
14
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Jun
14
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Apr
28
awarded  Nice Answer
Apr
28
comment The existence of non-trivial homomorphisms $\prod_{n=1}^{\infty}\mathbb{Z}/\bigoplus_{n=1}^{\infty}\mathbb{Z}\to\mathbb{Z}/p\mathbb{Z}$
Nice. Alternatively, we can think of the last displayed item as a ring $R$, every element of which satisfies the equation $x^p=x$. So if $I$ is any maximal ideal of $R$, then the elements of the field $R/I$ all satisfy the same equation, whence $R/I$ is the $p$-element field.