Solution: There are nine across entries that contain number prefixes (I used the Greek ones) in order- 15A MONO, 16A DI, 21A TRI, 23A TETRA, 33A PENTA, 49A HEXA, 50A HEPTA, 60A OCTO, 61A ENNEA. The next prefix is DECA, and the cocktail that I’m thinking of that contains DECA is SIDECAR. Not sure if there are others, but I’ll definitely give credit if you find one.