SQL & PL/SQL :: Show Grouped Data - Extract Subsets In Same Query

the point is that I have a table with two columns and I am trying to find and easy way to show grouped data.

CREATE TABLE TEST_DATA(C1 VARCHAR2(1), C2 VARCHAR2(2));

INSERT INTO TEST_DATA VALUES('1','A1');
INSERT INTO TEST_DATA VALUES('1','A2');
INSERT INTO TEST_DATA VALUES('1','A3');

[Code] .....

With the sample data there are 4 groups based in c1 column:

1 : A1,A2,A3
2 : A1,A2,A4
3 : A1,A2,A3
4 : A1,A2,A4
5 : A6,A7

I'm trying to get and output like :

A1,A2,A3 : 1,3
A1,A2,A4 : 2,4

I was trying something like :

select t1.c1 as gr1, t2.c1 as gr2, t1.c2
from test_data t1,test_data t2
where t1.c1<>t2.c1 and t1.c2=t2.c2
and
(select count(*) from test_data t3 where t3.c1=t1.c1)=
(select count(*) from test_data t4 where t4.c1=t2.c1)
order by 1 asc, 2 asc

but I don't find the way to refilter to group the data as expected. The idea is find subsets and show the set of data and values in column c1.