A100857 a(n) = greatest prime factor of (prime(n) - 1)! + prime(n).

3, 5, 29, 727, 3628811, 6599, 6385271, 1291883, 315389197, 123662437024088191, 2107707330310062524424576119, 50717732086848522419, 14602944428087660261, 55353784249983832172137, 16166897314580017

Offset: 1

Author

Reinhard Zumkeller, Nov 20 2004

Keywords

• nonn

Examples

			n=6: (prime(6)-1)! + prime(6) = 12! + 13 = 479001600 + 13 = 479001613 = 29*2503*6599, therefore a(6) = 6599.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..28 (using factordb.com)
• Dario A. Alpern, Factorization using the Elliptic Curve Method.
• FactorDB, Status of 109+108!.

Crossrefs

Cf. A006530, A100856, A100858.

Programs

Mathematica

FactorInteger[(#-1)!+#][[-1,1]]&/@Prime[Range[15]] (* Harvey P. Dale, Jul 23 2011 *)

Formula

a(n) = A006530(A100856(n)).

a(n) > A000040(n).