6300846559 is such that 6 is divisible by 2; 63, by 3; 630, by 5; 6300, by 7; and, in general, if you take its first N digits, it will be divisible by the N-th prime.
There is only one other such 10 digit number: can you find it?
(In reply to
re(2): Solution (VB program) by Penny)
The following code works in VB 5.0:
Dim prime(18)
Private Sub Command1_Click()
For i = 1 To 18
prime(i) = Choose(i, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61)
Next
Open "primediv.txt" For Output As #2
buildOn ""
Close 2
End Sub
Sub buildOn(s$)
l = Len(s$) + 1
had = 0
For i = 0 To 9
d$ = LTrim$(Str$(i))
s1$ = s$ + d$
v = Val(s1$)
q = Int(v / prime(l))
r = v - q * prime(l)
If r = 0 Then
had = 1
If l = UBound(prime) Then
Print #2, s1$; "*"
Else
buildOn s1$
End If
End If
Next i
If had = 0 Then
le$ = Right(" " + Str$(Len(s$)), 2) + " "
Print #2, le$; s$
End If
End Sub
The output was sent to a file as VB 5.0 has no console object. The resulting file was:
000000000000000000*
5 00077
7 0056168
9 030147871
5 03080
5 03509
6 035750
6 060281
6 060944
5 06512
9 065897139
6 090311
8 09526467
7 0959276
4 2100
9 210769470
8 21560592
7 2401369
4 2408
7 2450890
5 24574
6 270270
6 270933
7 2751195
8 27588627
8 42009551
7 4207585
4 4256
6 450125
7 4508927
8 45507812
5 45573
5 48026
6 480922
7 4851086
7 4858753
6 600600
7 6055536
10 6300846559
7 6307476
5 63569
6 660114
7 6608818
9 665067264
5 66572
5 69025
6 690911
4 6951
7 6958644
4 8106
8 81554270
8 84007379
8 84073670
6 845689
6 870103
7 8708709
7 8750563
10 8757193191
The asterisk after 000000000000000000 indicates that recursion was stopped deliberately. Otherwise recursion would go on forever and of course run out of stack space.
In QuickBasic, a DOS program under a Command Prompt, extra stack space was made using
CLEAR , , 5000
but I'm sure Windows programs in VB have more stack space to begin with. Just be sure that stack levels do not run out of hand.
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Posted by Charlie
on 2005-01-04 18:29:01 |
re(3): Solution (VB program)
