A164314 Largest prime factor of n^2 - 2.

2, 7, 7, 23, 17, 47, 31, 79, 7, 17, 71, 167, 97, 223, 127, 41, 23, 359, 199, 439, 241, 31, 41, 89, 337, 727, 23, 839, 449, 137, 73, 1087, 577, 1223, 647, 1367, 103, 31, 47, 73, 881, 1847, 967, 17, 151, 2207, 1151, 2399, 1249, 113, 193, 401, 47, 3023, 1567, 191

Offset: 2

Author

Vladimir Joseph Stephan Orlovsky, Aug 12 2009

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 2..10000

Crossrefs

Cf. A002583, A014442, A069902.

Programs

Maple

a:= n-> max(numtheory[factorset](n^2-2)):
seq(a(n), n=2..60);  # Alois P. Heinz, Jul 22 2017

Mathematica

Table[FactorInteger[n^2 - 2][[-1, 1]], {n, 2, 57}] (* Michael De Vlieger, Jul 22 2017 *)

PARI

a(n) = vecmax(factor(n^2-2)[,1]); \\ Michel Marcus, Jul 22 2017

Formula

a(n) = A006530(A008865(n)).

Extensions

Offset corrected by R. J. Mathar, Aug 21 2009