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A181460
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Numbers n such that 47 is the largest prime factor of n^2-1.
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3
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46, 48, 93, 95, 142, 187, 189, 281, 375, 377, 424, 469, 610, 657, 659, 704, 751, 753, 892, 988, 1033, 1035, 1082, 1174, 1223, 1270, 1364, 1409, 1597, 1599, 1691, 1693, 1926, 1973, 1975, 2022, 2069, 2161, 2255, 2351, 2443, 2584, 2727, 2913, 2915, 3009
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OFFSET
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1,1
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COMMENTS
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Sequence is finite, for proof see A175607.
Search for terms can be restricted to the range from 2 to A175607(15) = 2218993446251; primepi(47) = 15.
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LINKS
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MATHEMATICA
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Select[Range[300000], FactorInteger[#^2-1][[-1, 1]]==47&]
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PROG
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(Magma) [ n: n in [2..300000] | m eq 47 where m is D[#D] where D is PrimeDivisors(n^2-1) ]; // Klaus Brockhaus, Feb 19 2011
(PARI) is(n)=n=n^2-1; forprime(p=2, 43, n/=p^valuation(n, p)); n>1 && 47^valuation(n, 47)==n \\ Charles R Greathouse IV, Jul 01 2013
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CROSSREFS
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KEYWORD
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fini,nonn
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AUTHOR
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STATUS
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approved
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