Efficiently decoding a four bit input pattern into one of 16 twelve-bit output patterns
You can use an SRAM or a PROM for this. 4 input bits, 12 bits wide. Store your patterns in the memory, use the 4 input bits as the address.

There are 16 word SRAM ICs for this purpose. They would be useless to store "real" data, but are designed for arbitrary lookup tables and implementing simple logic.