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

1,1

Links

Table of n, a(n) for n=1..24.

Formula

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

Mathematica

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

Prog

(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

Crossrefs

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

Sequence in context: A041047 A120494 A038601 * A114747 A041639 A006985

Adjacent sequences: A372225 A372226 A372227 * A372229 A372230 A372231

Keyword

nonn

Author

Tyler Busby, Apr 23 2024

Status

approved