The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A252661 Numbers m such that 8^m - m is a semiprime. 2
 2, 7, 9, 111, 129, 133, 361 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(8) >= 369. - Hugo Pfoertner, Aug 03 2019 LINKS factordb.com, Status of 8^369-369. EXAMPLE 2 is in this sequence because 8^2-2 = 2*31 is semiprime. 9 is in this sequence because 8^9-9 = 23*5835553 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]; CROSSREFS Cf. similar sequences listed in A252656. Sequence in context: A079942 A272412 A042561 * A041453 A042157 A012937 Adjacent sequences: A252658 A252659 A252660 * A252662 A252663 A252664 KEYWORD nonn,more,hard AUTHOR Vincenzo Librandi, Dec 21 2014 EXTENSIONS a(4)-a(7) from Hugo Pfoertner, Aug 03 2019 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified March 25 08:54 EDT 2023. Contains 361520 sequences. (Running on oeis4.)