create or replace function GetPin return varchar2 as
l_pin number;

function IsCorrect(p_pin number) return boolean as
l_d1   number;
l_d2   number;
l_d3   number;
l_d4   number;
l_sign number;
begin
    l_d1 := trunc(    p_pin / 1000       );
    l_d2 := trunc(mod(p_pin,  1000) / 100);
    l_d3 := trunc(mod(p_pin,  100)  / 10 );
    l_d4 :=      (mod(p_pin,  10 )       );

    l_sign := sign(l_d1 - l_d2);

    if (l_d1 = l_d2 and l_d2 = l_d3 and l_d3 = l_d4) or
       (l_sign = sign(l_d2 - l_d3) and l_sign = sign(l_d3 - l_d4) and abs(l_d1 - l_d2) = 1 and abs(l_d2 - l_d3) = 1 and abs(l_d3 - l_d4) = 1) then
        return false;
    end if;

    return true;
end;

begin
    loop
        l_pin := trunc(dbms_random.value(1000, 9999));
        exit when IsCorrect(l_pin);
    end loop;

    return to_char(l_pin);
end;
/

Функция создана.

Затрач.время: 00:00:00.05

select GetPin
from dual
connect by level <= 30;

GETPIN
-----------------------------------------------------------------------------------------------------------------------------------------------------
8680
9276
6812
6502
9067
5375
8993
7976
7136
4704
4498
9560
3015
3173
4105
3069
3960
8859
4736
9515
9516
1937
6398
7136
2491
2850
3779
2166
4546
9160

30 строк выбрано.