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 A252793 Numbers m such that 8^m + m is a semiprime. 1
 1, 3, 5, 7, 11, 15, 21, 25, 75, 107, 221, 257, 273 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Next terms: 347?, 479, 521, 551, .... - Charles R Greathouse IV, Aug 17 2015 LINKS FORMULA 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. MATHEMATICA Select[Range[70], PrimeOmega[8^# + #]==2 &] PROG (MAGMA) IsSemiprime:=func; [m: m in [1..70] | IsSemiprime(s) where s is 8^m+m]; (PARI) is(n)=bigomega(8^n+n)==2 \\ Charles R Greathouse IV, Aug 14 2015 CROSSREFS Cf. similar sequences listed in A252788. Cf. A252661. Sequence in context: A337217 A333380 A177139 * A062488 A316936 A116582 Adjacent sequences:  A252790 A252791 A252792 * A252794 A252795 A252796 KEYWORD nonn AUTHOR Vincenzo Librandi, Dec 25 2014 EXTENSIONS a(9)-a(10) from Luke March, Jul 26 2015 a(11) from Carl Schildkraut, Aug 14 2015 a(12)-a(13) from Charles R Greathouse IV, Aug 17 2015 STATUS approved

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Last modified September 26 16:43 EDT 2020. Contains 337374 sequences. (Running on oeis4.)