create table iiii(n integer);
delete from iiii;
CREATE OR REPLACE FUNCTION fibonacci (n INTEGER)
RETURNS INTEGER AS $$
DECLARE
counter INTEGER := 0 ;
i INTEGER := 0 ;
j INTEGER := 1 ;
BEGIN
IF (n < 1) THEN
RETURN 0 ;
END IF;

LOOP
EXIT WHEN counter = n ;
counter := counter + 1 ;
SELECT j, i + j INTO i, j ;
insert into iiii values(j);
END LOOP ;

RETURN i ;
END ;
$$ LANGUAGE plpgsql;

select fibonacci(10)

select * from iiii