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A259026
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Numbers n such that n*23^n-1 is semiprime.
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0
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1, 2, 6, 8, 18, 21, 24, 26, 28, 30, 33, 230
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OFFSET
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1,2
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COMMENTS
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After 290, which may or may not be in the sequence, 420 and 450 are definitely in the sequence.
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LINKS
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MATHEMATICA
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Select[Range[200], PrimeOmega[# 23^# - 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..200] | IsSemiprime(s) where s is n*23^n-1];
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CROSSREFS
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Similar sequences listed in A242273.
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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