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.