I came across one which made me do a double take the other day whilst looking at line numbers of B777s.
LN #403 happens to be HL7700. It's registered to Asiana and currently active.
I'd have thought they might avoid a sequence like that - a bit like not having a number 13 in a street of houses?
(although ironically, it's LN #404 which had the bad luck - that one's 9M-MRO)