A372228 a(n) is the largest prime factor of n^n + n.

2, 3, 5, 13, 313, 101, 181, 5419, 21523361, 52579, 212601841, 57154490053, 815702161, 100621, 4454215139669, 4562284561, 52548582913, 1895634885375961, 211573, 2272727294381, 415710882920521, 9299179, 1853387306082786629, 22496867303759173834520497

Offset: 1

Author

Tyler Busby, Apr 23 2024

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..116

Crossrefs

Cf. A066068, A006530, A006486, A007571, A372229.

Programs

Mathematica

Table[f = FactorInteger[n^n + n]; f[[Length[f]]][[1]], {n, 1, 25}] (* Vaclav Kotesovec, Apr 26 2024 *)

Python

from sympy import primefactors
def A372228(n): return max(max(primefactors(n),default=1),max(primefactors(n**(n-1)+1))) # Chai Wah Wu, Apr 27 2024

Formula

a(n) = A006530(A066068(n)).