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
singletable. 
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