We investigate arithmetic properties of an overpartition counting function that first
arose in connection with Schur’s partition theorem and a universal mock theta function.
Motivated by work of Basil Gordon on the Rogers–Ramanujan identities, we first give a
complete characterization of the parity of this overpartition function in the progressions
,
, and
in terms of the
factorization of
for certain
and
.
We then find similar characterizations of the residue modulo
in the
progressions
and
.
Finally, we prove some Ramanujan-type congruences modulo
. Our
proofs use basic facts about modular forms and some elementary algebraic number
theory.
Keywords
partitions, overpartitions, parity, eta-quotients, binary
quadratic forms