This is a lot trickier than I thought at first.

In column A, text or values not a result of formulas:

aaa
bbb
ccc
xxx
a12
b12
c12
yyy
aaa
bbb
ccc
a12
zzz
b12
c12

Delete entire row of the duplicated entries.

After code has run on column A:

xxx
yyy
zzz

Produces a list (keeps the associated row) of single entry items only, others and their row are deleted.

Thanks,
Howard