A139467 Largest prime factor of n! + 2n - 1.

2, 5, 11, 31, 43, 43, 163, 2689, 362897, 3628819, 179, 1908373, 800903, 101341, 13999747, 104099179, 10778406912001, 1300448327, 356961701, 62382102773760001, 10367823077693, 11437176299, 102338720137, 1971511284252461621, 4324853339, 25264139643338071514377, 4403101273925738843820461

Offset

1,1

Links

Robert Israel and Amiram Eldar, Table of n, a(n) for n = 1..60 (terms 1..57 from Robert Israel)

Florian Luca and Igor E. Shparlinski, On the largest prime factor of n! + 2^n - 1, Journal de Theorie des Nombres de Bordeaux 17 (2005), 859-870.

Formula

a(n) = A006530(A139464(n)). - Amiram Eldar, Feb 05 2020

Maple

seq(max(numtheory:-factorset(n!+2*n-1)), n=1..30); # Robert Israel, Jun 28 2018

Mathematica

a = {}; Do[k = n! + 2 n - 1; c = First[Last[FactorInteger[k]]]; AppendTo[a, c], {n, 1, 40}]; a (*Artur Jasinski*)
Table[FactorInteger[n!+2n-1][[-1, 1]], {n, 30}] (* Harvey P. Dale, Aug 31 2011 *)

Prog

(PARI) a(n)=my(f=factor(n!+2*n-1)[, 1]); f[#f] \\ Charles R Greathouse IV, Feb 01 2013

Crossrefs

Cf. A006530, A127986, A127987, A139023, A139024, A139464, A139465, A139466.

Sequence in context: A390135 A139466 A291139 * A124481 A002862 A380990

Adjacent sequences: A139464 A139465 A139466 * A139468 A139469 A139470

Keyword

nonn

Author

Artur Jasinski, Apr 22 2008

Extensions

More terms from Robert Israel, Jun 28 2018

Status

approved