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For questions about sequences of integers. References are often made to the online resource oeis.org.

22 votes
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Is every sequence that looks like an AP really an AP?

For each $n$, the differences $a_{n+1}-a_n$, $a_{n+2}-a_{n+1}$, and $a_{n+2}-a_n$ can only be divisible by powers of $2$ and primes less than or equal to $c$. Since $$ \frac{a_{n+2}-a_{n+1}}{a_{n+2}- …
Julian Rosen's user avatar
  • 9,061
5 votes

On vanishing of $p$-adic logarithms

The $p$-adic logarithm can be computed $$ \begin{align*} \log_p(2) &= \frac{1}{p-1}\log_p(2^{p-1})\\ &=\frac{1}{p-1}\sum_{n\geq 1}(-1)^{n-1} \frac{(2^{p-1}-1)^n}{n} \\ &\equiv -pF(p)\mod p^2. \end{ali …
Julian Rosen's user avatar
  • 9,061
4 votes

Sequences with integral means

Here are some bounds on the stable value $r(n)$, as well as the number of terms of the sequence that need to be calculated. The short version is that $$ \frac{\sqrt{2}}{2}\sqrt{n}+O(1)\leq r(n)\leq \f …
Julian Rosen's user avatar
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