For any relatively prime integers $r$ and $s$, let $a_{ r,s}(n)$ denote the number of $(r,s)$-regular partitions of a positive integer of $n$ into distinct parts. Prasad and Prasad (2018) proved many infinite families of congruences modulo 2 for $a_{ 3,5}(n)$. In this paper, we establish families of congruences modulo 2 and 4 for $a_{ r,s}(n)$ with $(r,s)\in$ \{ (2,5), (2,7), (4,5), (4,9)\}. For example, we show that for all $\beta \geq 0$ and $n \geq 0,$ we have $$a_{ 2,5}\Big(4\cdot 5^{ 2\beta+1}n+\dfrac{ 37\cdot5^{ 2\beta}-1}{ 6}\Big)\equiv0 \pmod4. $$
Categories: math.NT