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A252792
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Numbers m such that 7^m + m is a semiprime.
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1
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2, 3, 6, 12, 15, 16, 30, 54, 244, 850, 1488
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OFFSET
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1,1
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LINKS
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EXAMPLE
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2 is in this sequence because 7^2+2 = 3*17 is semiprime.
6 is in this sequence because 7^6+6 = 5*23531 and these two factors are prime.
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MATHEMATICA
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Select[Range[600], PrimeOmega[7^# + #]==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..600] | IsSemiprime(s) where s is 7^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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