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Primed to Square (Posted on 2013-02-15) Difficulty: 3 of 5
What is the largest prime p that makes sqrt(17p+625) an integer?

No Solution Yet Submitted by Danish Ahmed Khan    
Rating: 4.0000 (2 votes)

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Solution computer exploration (probable spoiler) | Comment 1 of 3

 5   P=1
10   while P<9999999999 and P>0
20     P=nxtprm(P)
30     N=17*P+625
40     Sr=int(sqrt(N)+0.5)
50     if Sr*Sr=N then print P;
60   wend

finds only 3 and 67 by the time the program was stopped at p = 82,150,333.


  Posted by Charlie on 2013-02-15 18:24:00
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