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x^r + a is prime

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  • cino hilliard
    Hi, A twist on the old x^y - y^x prime search is x^r + a where r is the reverse of the digits of x and a is an integer. See Pari code below For example
    Message 1 of 1 , Aug 22, 2009
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      Hi,



      A twist on the old x^y - y^x prime search is x^r + a where r is the reverse
      of the digits of x and a is an integer. See Pari code below



      For example

      g(1000,2)
      0,1,3,39,51,87,113,737,831,



      737^737+2 is a 2114 digit prime



      [PRIMO - Task Report]
      Version=3.0.7
      WebSite=http://www.ellipsa.net/
      Task=Certification
      ID=B31C802C933B8
      Created=08/21/2009 12:59:00 PM

      [Common]
      Path=C:\primo\
      Selected=1
      Processed=1
      Certified=1
      Candidate #1=Certified, 18h 53mn 59s

      [Candidate #1]
      Input=737to737+2.in
      Report=primo-B31C802C933B8-001.cr
      Output=primo-B31C802C933B8-001.out
      Status=Candidate certified prime





      Pari code



      g(n,a) = for(x=0,n,r=eval(rev(x));y=x^r+a;if(ispseudoprime(y),print1(x",")))



      rev(str)=local(tmp,s,j);tmp=Vec(Str(str));s="";forstep(j=length(tmp),1,-1,

      s=concat(s,tmp[j]));return(s)





      Cino










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