2 problems

Let $k$ be a positive integer, let $\partial$ denote differentiation, and let $a_j,a_m\in\mathbb C$. For a divisor $\ell$ of $k$, define … with $a_{\ell-1}\neq0$, and let $q(t)$ be…

Let $L$ be an irreducible differential operator of order $k$ solving the generalized Bochner–Krall problem, and let $\Lambda$ be its corresponding difference operator. Order-preser…