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A242204
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Numbers n such that n*4^n+1 is semiprime.
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1
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2, 6, 8, 9, 13, 15, 25, 36, 37, 63, 66, 72, 73, 85, 205, 333, 430
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OFFSET
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1,1
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COMMENTS
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The semiprimes of this form are: 33, 24577, 524289, 2359297, 872415233, 16106127361, 28147497671065601, 170005193383307227693057, 698910239464707491627009, ...
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LINKS
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MATHEMATICA
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Select[Range[120], PrimeOmega[# 4^# + 1] == 2 &]
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PROG
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(Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [n: n in [1..110] | IsSemiprime(s) where s is n*4^n+1];
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CROSSREFS
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Cf. similar sequences listed in A242203.
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KEYWORD
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nonn,more,hard
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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