A080798 Largest prime factor of 3^n-2.

7, 5, 79, 241, 727, 23, 937, 19681, 431, 499, 4703, 8093, 40193, 2869781, 483671, 94747, 4657, 232452293, 498112057, 2812679, 31381059607, 3765727153, 1364071, 44594137339, 125231, 13170403, 5353801183, 4159349, 46050353857, 294487079, 26892769, 29178816413, 3533781113

Offset: 2

Author

Hugo Pfoertner, Mar 25 2003

Keywords

• nonn

Links

• Hugo Pfoertner, Table of n, a(n) for n = 2..210

Crossrefs

Cf. A014224, A014232, A080443, A080892.

Cf. A006530, A058481.

Programs

Magma

[Max(PrimeDivisors(3^n-2)):n in [2..30]]; // Marius A. Burtea, Jul 12 2019

Mathematica

FactorInteger[#][[-1,1]]&/@(3^Range[2,30]-2) (* Harvey P. Dale, Apr 07 2022 *)

PARI

a(n) = vecmax(factor(3^n-2)[,1]); \\ Michel Marcus, Jul 12 2019

Formula

a(n) = A006530(A058481(n)). - Michel Marcus, Jul 12 2019