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A252793
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Numbers m such that 8^m + m is a semiprime.
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1
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1, 3, 5, 7, 11, 15, 21, 25, 75, 107, 221, 257, 273
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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1 is in this sequence because 8^1+1 = 3*3 is semiprime.
7 is in this sequence because 8^7+7 = 3*699053 and these two factors are prime.
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MATHEMATICA
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Select[Range[70], PrimeOmega[8^# + #]==2 &]
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PROG
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(Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [m: m in [1..70] | IsSemiprime(s) where s is 8^m+m];
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CROSSREFS
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Cf. similar sequences listed in A252788.
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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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