User blog comment:Rgetar/Ordinal Explorer Online/@comment-44238981-20200214192953/@comment-32213734-20200216122007

I think that
 * M = [[c]c][[c]cc] = [c2][c2c] = [[[c2]L]c] = [[L2]c] = [c + L2]

At least currently [[c]c][[c]cc] is designatied as "M" in the 2nd and 3rd formats.