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

3,1

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)

Formula

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

Example

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.

Mathematica

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

Prog

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

Crossrefs

Cf. A000166, A006530.

Sequence in context: A184315 A020133 A086528 * A353726 A353727 A041441

Adjacent sequences: A152021 A152022 A152023 * A152025 A152026 A152027

Keyword

nonn

Author

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

Extensions

Corrected and extended by Michel Marcus, Jun 01 2013

Status

approved