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For questions about sequences of integers. References are often made to the online resource oeis.org.
3
votes
Accepted
Does the Kimberling sequence map numbers "arbitrarily far away"?
The answer is yes. Indeed, as noted at A007063,
$$k(\theta_j)=3\theta_j-(j+1),
$$
where
$$\theta_j:=\sum_{i=0}^{j-1}2^{\lfloor i/3\rfloor}\ge2^{\lfloor(j-1)/3\rfloor}.
$$
So,
$$k(\theta_j)-\theta_j …
3
votes
How many flips of a fair coin are needed to get at least one run of at least $k$ consecutive...
According to Mathworld (see also Wikipedia),
$$P_{k,n}=1-\frac{F_{k,n}}{2^n},\tag{1}$$
where, for each natural $k$, $(F_{k,n})_{n=1}^\infty$ is the sequence of $k$-step Fibonacci numbers, defined rec …
4
votes
Accepted
A binomial coefficient identity involving two parameters
Taking into account that $\binom pq=0$ for nonnegative integers $p$ and $q$ such that $q>p$, write
$$S(n,m)=\frac{(n+m+1)!}{n!m!}T(n,m),$$
where
\begin{align*}
T(n,m)&:=\sum_{l\ge0}\frac{1}{n+m-l+1} …
4
votes
Accepted
Bounds for the sequence $a(n)=a(n-1)+a(\lfloor n-n^A \rfloor)$
Let us show that
\begin{equation*}
a(n)\le\exp(n^{1-A+o(1)}) \tag{1}\label{1}
\end{equation*}
(as $n\to\infty$).
Indeed, for each $q\in(1-A,1)$,
\begin{equation*}
(k-1)^q-k^q\sim-qk^{q-1},\qua …
9
votes
Upper bound an integral with exponential function
The integral in question can be rewritten as
$$
\begin{aligned}
I&:=\frac1{\sqrt n}\,\int_{-a\sqrt n}^{(1-a)\sqrt n} e^{-u^2}\Big(1-\exp\Big\{-\frac{u^4/n}{1-u^2/n}\Big\}\Big)\,du \\
&\le\frac1{\sqrt …
4
votes
Accepted
Negated Fibonacci and the floor function
We have
$$F_{-n}=\frac{(-a_-)^n-(-a_+)^n}{\sqrt5} \tag{1}\label{1}$$
with
$$a_\pm:=\frac{1\pm\sqrt5}2.$$
We also have the easy formula for $\sum_{j=j_1}^{j_2}(p+qj)x^j$, which yields
$$\sum_{i=1}^{n-1 …
11
votes
What is the connection between these three methods of generating this sequence?
We will obtain simple explicit Fibonacci-like expressions for the feasible numbers of the red and white balls in the jar, which we will denote by
$r$ and $w$ respectively, with $n:=r+w$.
We have $\bin …