First we must introduce some musical terminology, with apologies to readers who are already familiar with it.
A time series is a sequence of values $x_1,x_2,x_3, \cdots$, usually representing measurements of some quantity at equal intervals of time.
Here is a problem of the sort that could possibly be set in a 4-unit paper:
In a recent article of Parabola (Vol. 25 No.3), Esther Szekeres showed how we could prove many geometrical results by thinking in terms of centers of mass.
Q.794 $A$ and $B$ are opposite vertices of a cube of side length 1 unit.
Q.782 Let $S_n = \frac{1}{1^2-\frac{1}{4}} + \frac{1}{2^2 - \frac{1}{4}}+ \frac{1}{3^2 - \frac{1}{4}} + \cdots + \frac{1}{n^2 - \frac{1}{4}}$. Simply this expression, and show that $n$ is large $S_n$ is approximately equal to 2.