New Identities in the Character Table of Symmetric Groups involving Riordan Numbers

Source abstract

Amdeberhan recently proposed certain equalities between sums in the character table of symmetric groups. These equalities are between signed column sums in the character table, summing over the rows labeled by partitions in $\mathrm{Ev}(\lambda)$, where $\lambda$ is a partition of $n$ with $r$ nonzero parts and $\mathrm{Ev}(\lambda)$ is a multiset containing $2^r$ partitions of $2n$. While we observe that these equalities are not true in general, we prove that they do hold in interesting special cases. These lead to new equalities between sums of degrees of irreducible characters for the symmetric group and a new combinatorial interpretation for the Riordan numbers in terms of degrees of irreducible characters labeled by partitions with three parts of the same parity. This is the first, to our knowledge, theorem about degrees of symmetric group characters with parity conditions imposed on the partitions indexing the characters.