A152024 Largest prime factor in the subfactorial of n.

2, 3, 11, 53, 103, 163, 41, 16481, 1468457, 1456321, 139241, 1796801, 34361893981, 15549624751, 461702183, 65026777, 893977617157, 17562703393, 482455223267, 85836476923, 352463, 809358677, 499243508845229, 1802157757041847990541

Offset: 3

Author

Albert Moes (albertmoes(AT)freeler.nl), Nov 20 2008

Keywords

• nonn

Examples

			For n=5 (the third member of the sequence), the number of derangements is 44, thus a(5) = 11, the largest prime factor of 44.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 3..81
• Dario Alpern, Factorization using the Elliptic Curve Method.
• Amiram Eldar, Table of prime factors of A000166(n) for n = 3..81 (calculated with Dario Alpern's ECM)

Crossrefs

Cf. A000166, A006530.

Programs

Mathematica

Table[FactorInteger[Subfactorial[n]][[-1, 1]], {n, 3, 30}] (* Amiram Eldar, Jul 31 2022 *)

PARI

a(n) = {fn = factor(round(n!/exp(1))); fn[#fn[, 1], 1]} \\ Michel Marcus, Jun 01 2013

Formula

a(n) = A006530(A000166(n)). - Amiram Eldar, Jul 31 2022

Extensions

Corrected and extended by Michel Marcus, Jun 01 2013