^not quite. It's DCXL. Never use 4 letters in a row.
DCXLI
DCXLII (642)
DCXLIII
DCXLIV
DCXLV
DCXLVI
DCXLVII
DCXLVIII
DCXLIX
DCL
DCLI
DCLII
DCLIII
DCLIV
DCLV
DCLVI
DCLVII
DCLVIII
DCLIX
DCLX