EN
Let $p̅_{o}(n)$ denote the number of overpartitions of n in which only odd parts are used. Some congruences modulo 3 and powers of 2 for the function $p̅_{o}(n)$ have been derived by Hirschhorn and Sellers, and Lovejoy and Osburn. In this paper, employing 2-dissections of certain quotients of theta functions due to Ramanujan, we prove some new infinite families of Ramanujan-type congruences for $p̅_{o}(n)$ modulo 3. For example, we prove that for n, α ≥ 0,
$p̅_{o}(4^{α}(24n+17)) ≡ p̅_{o}(4^{α}(24n+23)) ≡ 0 (mod 3)$.