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 A242337 Numbers k such that k*6^k-1 is semiprime. 1
 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15, 18, 22, 23, 25, 32, 35, 38, 45, 51, 54, 57, 68, 72, 82, 97, 110, 138, 155, 234, 254 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The semiprimes of this form are: 5183, 38879, 279935, 1959551, 90699263, 604661759, 3990767615, 26121388031, 169789022207, 1097098297343, ... LINKS MATHEMATICA Select[Range[352], PrimeOmega[# 6^# - 1]==2&] PROG (MAGMA) IsSemiprime:=func; [n: n in [2..352] | IsSemiprime(s) where s is n*6^n-1]; CROSSREFS Cf. similar sequences listed in A242273. Cf. A059675, A064752. Sequence in context: A068521 A196697 A068318 * A201739 A329782 A218044 Adjacent sequences:  A242334 A242335 A242336 * A242338 A242339 A242340 KEYWORD nonn,more AUTHOR Vincenzo Librandi, May 12 2014 EXTENSIONS a(26)-a(31) from Carl Schildkraut, Aug 17 2015 STATUS approved

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Last modified December 10 14:27 EST 2019. Contains 329896 sequences. (Running on oeis4.)