The Bulava missile that just made its maiden flight, has many different designations. The U.S. Department of Defense apparently calls it SS-NX-30 (which will become SS-N-30 after the missile is accepted for service). But in the START Treaty data exchange it is listed under its Russian "treaty name" RSM-56 unlike all other missiles, which use their "SS-N-" designations. The choice of RSM-56 would be in line with the existing sequence - RSM-50, RSM-52, and RSM-54.
Another name for the missile was mentioned by the Russian defense minister, who called it R-30. This would also be generally compatible with the R-sequence, which so far had a few R-29 missiles, R-31, and R-39.
Update: The index of the Bulava missile is 3M30.