> This uses one-byte characters encode seven bits and two-byte characters to encode fourteen bits. Hence this attains the goal of encoding seven bits per byte, i.e. the 8 : 7 inflation ratio.

The magic is in the 2 byte encoding 110sss1x 10xxxxxx.

There are really 890 characters used in this encoding, so it should be called base890.

((2^7)-6)+((6•2)•(2^6))=890