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A195008
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Numbers n such that there are no primes between n*sqrt(n-1) and (n+1)*sqrt(n).
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1
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1, 24, 36, 47, 93, 105, 109, 117, 122, 207, 627, 996
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OFFSET
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1,2
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COMMENTS
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Numbers n such that there are only nonprimes between n*sqrt(n-1) and (n+1)*sqrt(n).
No more terms up to 100000. - Franklin T. Adams-Watters, Sep 08 2011
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LINKS
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EXAMPLE
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a(1)=1 because 1*sqrt(1-1)=0<(nonprime 1)<(1+1)*sqrt(1)=2,
a(2)=24 because 24*sqrt(24-1)<(nonprimes 116,117,118,119,120,121)<(24+1)*sqrt(24).
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MATHEMATICA
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Join[{1}, Select[Range[1000], PrimePi[# Sqrt[#-1]]==PrimePi[(#+1)Sqrt[#]]&]] (* Harvey P. Dale, Jun 01 2018 *)
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PROG
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(PARI) isa(n)=if(n<=1, n==1, primepi(floor(n*sqrt(n-1)))==primepi(floor((n+1)*sqrt(n)))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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