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18 votes
1 answer
714 views

Is the p-adic density of the image of a polynomial always rational?

This question was previously posted here on MSE. Let $P(x)$ be a polynomial with integer coefficients, and let $p$ be a prime number. For $n\in\mathbb N$, let $I_n$ be the number of integers $i\in\{1,\...
Riemann's user avatar
  • 654
12 votes
1 answer
841 views

Numbers $k$ with $\{\binom nk:\ n\in\mathbb N\}$ dense in $\mathbb Z_p$ for any prime $p\le k$

Let $k$ be a positive integer and let $p$ be a prime. In my 2011 PAMS paper joint with my former student W. Zhang [Proc. Amer. Math. Soc. 139(2011), 1569-1577], we studied when $$S(k)=\left\{\binom nk:...
Zhi-Wei Sun's user avatar
  • 15.6k
7 votes
2 answers
606 views

convergence in $\hat{\mathbb{Z}}$, modulo prime power

The following problem appears in Lenstra's Galois Theory for Schemes (p 14, Ex 1.16). Let $b\in\mathbb Z_{\ge0}$. Define the sequence $(a_n)_{n=0}^\infty$ by $a_0=b, a_{n+1}=2^{a_n}$. Prove that $...
Michael's user avatar
  • 101