Bell-shaped sequences
Mateusz Kwaśnicki, Jacek Wszoła · Studia Mathematica · 2023
A nonnegative real function $f$ is said to be bell-shaped if it converges to zero at $\pm \infty $, and the $n$th derivative of $f$ changes sign $n$ times for every $n = 0, 1, 2, \ldots $ In a similar way, we may say that a nonnegative sequence $a_k$ is b