If you're willing to accept address aliasing (i.e. chips appearing at more than one memory address) you can simply use multiple '138 decoders in parallel to make a 1-of-24 or 1-of-32 decoder. In fact that's precisely why the '138 has so many enable inputs: the one active high (G1) and two active low (~G2A and ~G2B)enable inputs let you build a 1-of-24 decoder using three '138 chips and zero additional glue.