A281793 The largest prime factor of (1+n)*(1+n^2).

1, 2, 5, 5, 17, 13, 37, 5, 13, 41, 101, 61, 29, 17, 197, 113, 257, 29, 19, 181, 401, 17, 97, 53, 577, 313, 677, 73, 157, 421, 53, 37, 41, 109, 89, 613, 1297, 137, 17, 761, 1601, 29, 353, 37, 149, 1013, 73, 17, 461, 1201, 61, 1301, 541, 281, 2917, 89, 3137, 29

Offset: 0

Author

R. J. Mathar, Jan 30 2017

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Crossrefs

Cf. A006530, A014442, A281660.

Programs

Magma

[#f eq 0 select 1 else f[ #f][1] where f is Factorization((1+n)*(1+n^2)): n in [0..60]]; // Vincenzo Librandi, Jun 03 2017

Maple

A281793 := proc(n)
    A006530((1+n)*(1+n^2)) ;
end proc:
seq(A281793(n),n=0..60) ;

Mathematica

Table[Max[Transpose[FactorInteger[(1 + n) (1 + n^2)]][[1]]], {n, 0, 60}] (* Vincenzo Librandi, Jun 03 2017 *)

PARI

a(n) = if (n==0, 1, my(f=factor((1+n)*(1+n^2))); vecmax(f[, 1])); \\ Michel Marcus, Jun 03 2017; corrected Jun 13 2022

Formula

a(n) = max( A006530(n+1), A014442(n)).

a(n) = A006530(A281660(n)).