Proof of a conjecture of Das on the coefficients of mock theta functions

Ramanujan recorded seventeen mock theta functions in his last letter to Hardy. Quite recently, Das (J Math Anal Appl 543(2):128913, 2025) proved some congruences modulo small powers of 3 between the coefficients of the second order mock theta functions μ2(q) and A2(q), introduced by Ramanujan and McIntosh, respectively. Moreover, Das conjectured a congruence modulo 2187 and three congruences modulo 6561 between the coefficients of μ2(q) and A2(q). In this paper, we prove these conjectural congruences by employing some q-series manipulations. Further, we conjecture an infinite family of congruences modulo high powers of 3 between the coefficients of μ2(q) and A2(q). © The Author(s) under exclusive licence to The Royal Academy of Sciences, Madrid 2025.