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A181448
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Numbers n such that 5 is the largest prime factor of n^2 - 1.
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2
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OFFSET
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1,1
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COMMENTS
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Sequence is finite and complete, for proof see A175607.
Search for terms can be restricted to the range from 2 to A175607(3) = 161; primepi(5) = 3.
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LINKS
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MATHEMATICA
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Select[Range[200], FactorInteger[#^2-1][[-1, 1]]==5&]
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PROG
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(Magma) [ n: n in [2..200] | m eq 5 where m is D[#D] where D is PrimeDivisors(n^2-1) ]; // Klaus Brockhaus, Feb 17 2011
(PARI) is(n)=n=n^2-1; n>>=valuation(n, 2); n/=3^valuation(n, 3); n>1 && 5^valuation(n, 5)==n \\ Charles R Greathouse IV, Jul 01 2013
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CROSSREFS
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KEYWORD
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fini,full,nonn
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AUTHOR
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STATUS
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approved
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