function returning a merge of the same query executed X time

Hi all,
I'm having difficulties to create a function that should execute X time the same query and return their results as a single table.
I tried this way but it don't work :
Thanks to help.

create function cm_get_json_loop_info(
IN profile integer,
IN distance double precision DEFAULT 10,
IN x_start double precision DEFAULT 0,
IN y_start double precision DEFAULT 0,
IN nbr integer default 1)

returns setof json as
$BODY$
declare jsona json;
BEGIN
for json a i in 1.. nbr loop

select row_to_json(q)
from (select row_number() over() as id, sum(cost) as total_cost,sum(length) as total_length,json_agg(row_to_json(r)) as data
from (select * from cm_get_loop_route_4(2, 10, -73.597070, 45.544083))r)q
return next jsona
end loop;
return jsona;

Marc