100 REM Moebius function
110 DECLARE EXTERNAL FUNCTION Moebius
120 FOR T = 0 TO 9
130    FOR U = 1 TO 10
140       PRINT USING "##  ": Moebius(10 * T + U);
150    NEXT U
160    PRINT
170 NEXT T
180 END
190 REM ***
200 EXTERNAL FUNCTION Moebius(N)
210 LET M = 1
220 IF N <> 1 THEN
230    LET F = 2
240    DO
250       IF MOD(N, (F * F)) = 0 THEN
260          LET M = 0
270       ELSE
280          IF MOD(N, F) = 0 THEN
290             LET M = -M
300             LET N = N / F
310          END IF
320          LET F = F + 1
330       END IF
340    LOOP WHILE (F <= N) AND (M <> 0)
350 END IF
360 LET Moebius = M
370 END FUNCTION