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 A252792 Numbers m such that 7^m + m is a semiprime. 1
 2, 3, 6, 12, 15, 16, 30, 54, 244 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(10) > 600. - Carl Schildkraut, Aug 14 2015 LINKS EXAMPLE 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. MATHEMATICA Select[Range[600], PrimeOmega[7^# + #]==2 &] PROG (MAGMA) IsSemiprime:=func; [m: m in [1..600] | IsSemiprime(s) where s is 7^m+m]; CROSSREFS Cf. similar sequences listed in A252788. Cf. A252660. Sequence in context: A329401 A291174 A281110 * A284638 A111271 A217647 Adjacent sequences:  A252789 A252790 A252791 * A252793 A252794 A252795 KEYWORD nonn,more AUTHOR Vincenzo Librandi, Dec 25 2014 EXTENSIONS a(9) from Carl Schildkraut, Aug 14 2015 STATUS approved

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Last modified September 22 22:24 EDT 2020. Contains 337291 sequences. (Running on oeis4.)