A136031 Largest prime factor of composite Mersenne numbers.

89, 178481, 2089, 616318177, 164511353, 2099863, 13264529, 20394401, 3203431780337, 761838257287, 212885833, 9361973132609, 1113491139767, 57912614113275649087721, 13842607235828485645766393, 341117531003194129, 3976656429941438590393

Offset: 1

Author

Artur Jasinski, Dec 11 2007

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..183

Crossrefs

Cf. A049479, A016047, A003260, A136030.

Programs

Mathematica

FactorInteger[2^#-1][[-1,1]]&/@Select[Prime[Range[40]],!PrimeQ[2^#-1]&] (* Harvey P. Dale, May 05 2012 *)
With[{c=Complement[Prime[Range[PrimePi[200]]],MersennePrimeExponent[ Range[ 15]]]},Table[ FactorInteger[ 2^p-1][[-1,1]],{p,c}]] (* Harvey P. Dale, Sep 06 2021 *)

Formula

a(n) >= A089158(n). - R. J. Mathar, May 01 2008

Extensions

Corrected by Harvey P. Dale, May 05 2012