DECLARE SUB Mult2 ()
DECLARE SUB ShowNum ()
DECLARE FUNCTION dMod# (a#, b#)
DEFINT A-Z
DIM SHARED a(1 TO 1000) AS DOUBLE, np, dec, nfermat
DIM SHARED b(1 TO 1000) AS DOUBLE
CLS
nfermat = 16
dec = 9
a(1) = 1: np = 1
FOR i& = 1 TO 2 ^ nfermat
   LOCATE 1, 1: PRINT USING "#####> "; i&;
   Mult2
   LOCATE 2, 1
   SELECT CASE INKEY$
      CASE CHR$(27): EXIT FOR
      CASE " ": ShowNum
   END SELECT
NEXT
a(1) = a(1) + 1
ShowNum
FOR i = 1 TO np: b(i) = a(i): NEXT
FOR k& = 1 TO 100000
   LOCATE 5, 1: PRINT k&;
   div# = 2# ^ (nfermat + 2) * k& + 1
   PRINT div#;
   IF div# >= 10# ^ dec THEN PRINT "Max"; : SYSTEM
   FOR i = 1 TO np: a(i) = b(i): NEXT
   FOR i = np TO 1 STEP -1
      x# = INT(a(i) / div#)
      y# = dMod(a(i), div#)
      a(i) = x#
      IF y# > 0 THEN
         IF i = 1 THEN
            PRINT "Ndiv"; : er = -1: EXIT FOR
         ELSE
            a(i - 1) = a(i - 1) + y# * 10# ^ dec
         END IF
      END IF
   NEXT
   IF er THEN er = 0 ELSE ShowNum: SYSTEM
   IF INKEY$ <> "" THEN EXIT FOR
NEXT
SYSTEM

FUNCTION dMod# (a#, b#)
d# = ((a# / b#) - INT(a# / b#)) * b#
IF d# < 1D-35 THEN d# = 0
dMod# = d#
END FUNCTION

SUB Mult2
nbase# = 10# ^ dec
FOR i = 1 TO np
   a(i) = a(i) * 2
NEXT
FOR i = 1 TO np
   x = INT(a(i) / nbase#)
   IF x > 0 THEN
      y# = dMod(a(i), nbase#)
      a(i + 1) = a(i + 1) + x
      a(i) = y#
   END IF
NEXT
IF x > 0 THEN np = np + 1
END SUB

SUB ShowNum
x$ = ""
FOR i = np TO 1 STEP -1
   IF a(i) > 0 OR i < np THEN
      PRINT RIGHT$(x$ + LTRIM$(STR$(a(i))), dec);
      x$ = STRING$(dec, "0")
   END IF
NEXT
END SUB