If I understand correctly this ?

Entered in B1 and filled down.

=NOT(A1=INDEX($A$1:$A$10,MATCH(1,FREQUENCY($A$1:$A$10,$A$1:$A$10),0)))



A
B
1
2
TRUE
2
2
TRUE
3
2
TRUE
4
2
TRUE
5
3
FALSE
6
2
TRUE
7
2
TRUE
8
2
TRUE
9
2
TRUE
10
2
TRUE