A093817 Largest prime factor of 2^n-3.

1, 5, 13, 29, 61, 5, 23, 509, 1021, 409, 4093, 431, 16381, 6553, 71, 2473, 23831, 97, 1048573, 2713, 4194301, 1677721, 16777213, 70051, 5197, 31033, 1877171, 536870909, 46684427, 22605091, 464773, 296204641, 3360037, 6871947673, 283007

Offset: 2

Author

Yasutoshi Kohmoto, May 11 2004

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 2..626 (terms 2..200 from Vincenzo Librandi)

Crossrefs

Cf. A006530, A036563, A050414, A050415, A093810.

Programs

Mathematica

PrimeFactors[n_] := Flatten[ Table[ # [[1]], {1}] & /@ FactorInteger[n]]; Table[ PrimeFactors[2^n - 3][[ -1]], {n, 2, 46}] (* Robert G. Wilson v, May 24 2004 *)
Table[FactorInteger[2^n-3][[-1,1]],{n,2,40}] (* Harvey P. Dale, Feb 01 2015 *)

Formula

a(n) = A006530(A036563(n)). - Amiram Eldar, Sep 12 2022

Extensions

More terms from Robert G. Wilson v, May 24 2004