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A252791
Numbers m such that 6^m + m is a semiprime.
1
2, 3, 5, 7, 11, 23, 41, 55, 73, 91, 131, 199, 221, 287
OFFSET
1,1
COMMENTS
From Kevin P. Thompson, May 01 2022: (Start)
a(15) >= 335.
391, 443, 607, 683, 737, and 745 are also terms in this sequence. (End)
EXAMPLE
2 is in this sequence because 6^2+2 = 2*19 is semiprime.
7 is in this sequence because 6^7+7 = 271*1033 and these two factors are prime.
MATHEMATICA
Select[Range[90], PrimeOmega[6^# + #]==2 &]
PROG
(Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [m: m in [1..90] | IsSemiprime(s) where s is 6^m+m];
CROSSREFS
Cf. similar sequences listed in A252788.
Cf. A252659.
Sequence in context: A288371 A158217 A030284 * A068148 A036344 A165802
KEYWORD
nonn,more
AUTHOR
Vincenzo Librandi, Dec 25 2014
EXTENSIONS
a(10)-a(14) by Luke March, Jul 08 2015
STATUS
approved