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A242335
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Numbers k such that k*4^k-1 is semiprime.
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1
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10, 12, 18, 24, 27, 44, 47, 65, 71, 82, 84, 131, 134, 138, 143, 155, 164, 168, 197, 212, 227, 243, 248, 293, 302, 384, 401
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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: 10485759, 201326591, 1236950581247, 6755399441055743, 486388759756013567, 13617340432139183023890366463, ...
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LINKS
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MATHEMATICA
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Select[Range[100], 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 [2..100] | IsSemiprime(s) where s is n*4^n-1];
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CROSSREFS
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Cf. similar sequences listed in A242273.
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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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