Select
   A.RDB$INDEX_NAME as INDICE_1,
   B.RDB$INDEX_NAME as INDICE_2

from RDB$INDICES A

inner join RDB$INDICES B on
   A.RDB$RELATION_NAME = B.RDB$RELATION_NAME and
   A.RDB$INDEX_NAME    < B.RDB$INDEX_NAME

where
   A.RDB$SEGMENT_COUNT = B.RDB$SEGMENT_COUNT and
   coalesce(A.RDB$UNIQUE_FLAG, 0) = coalesce(B.RDB$UNIQUE_FLAG, 0) and
   coalesce(A.RDB$INDEX_TYPE,  0) = coalesce(B.RDB$INDEX_TYPE,  0) and
   ( A.RDB$EXPRESSION_BLR=B.RDB$EXPRESSION_BLR
      or
     A.RDB$SEGMENT_COUNT = ( Select
                                COUNT(*)
                             from RDB$INDEX_SEGMENTS AA
                             inner join RDB$INDEX_SEGMENTS BB on
                                 AA.RDB$FIELD_POSITION=BB.RDB$FIELD_POSITION and
                                 AA.RDB$FIELD_NAME=BB.RDB$FIELD_NAME and
                                 AA.RDB$INDEX_NAME=A.RDB$INDEX_NAME and
                                 BB.RDB$INDEX_NAME=B.RDB$INDEX_NAME
                           )
   )