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Spirit of '76 (Posted on 2004-03-14) Difficulty: 3 of 5
Can you find a 76-digit multiple of 276, written exclusively with 7s and 6s?

See The Solution Submitted by Federico Kereki    
Rating: 4.2500 (8 votes)

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calculations provided by ... | Comment 6 of 8 |
(In reply to more thoughts (actually solution--spoiler) by Charlie)

The random-choice method, carried out far enough for the solution, was found using:

   10   D=2^76
   15   Pow=10:Num=6
   20   repeat
   25       Fl=0
   28       if rnd>0.5 then Bg=9:Nd=0:Stp=-1:else Bg=0:Nd=9:Stp=1
   30       for I=Bg to Nd step Stp
   40          Trial=Num+I*Pow
   50          if Fl=0 and (((Trial*D)@(10*Pow))\Pow=6 or ((Trial*D)@(10*Pow))\Pow=7) then
   60               :Num=Trial:Pow=Pow*10:Fl=1
   70       next
   80   *Foundit
   85       print:print Trial,Trial*D
   90   until Num>10^100
  100   N=(Trial*D)@10^76
  110   print N,N@D


  Posted by Charlie on 2004-03-14 13:59:50
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