Duplicate values identification

Christ.

I know the way to do it for a small table

=if(countif([C1]:[C1],[C1]@row)>1,"Red","")

But that cell reference all the cells in C1. It get to a huge number of reference quickly.

I've reached the 250 000 limit with that and around 4k rows.

Is there a different way that use less cell references ?

Christ.

10 rows = 10^2 reference = 100 references

4000 rows = 4000^2 = 16 000 000 references