A127990 Largest prime factor of 2*n^3 - 2*n + 9.

3, 7, 19, 43, 83, 13, 227, 113, 23, 17, 883, 37, 1459, 1823, 2243, 389, 11, 431, 13, 5323, 6163, 373, 89, 9203, 103, 83, 257, 443, 439, 367, 19843, 73, 647, 26183, 9521, 797, 1607, 36559, 3593, 42643, 2417, 49367, 1709, 53, 173, 7207, 1609, 73699, 163, 7573

Offset: 1

Author

Artur Jasinski, Feb 10 2007

Keywords

• nonn

Comments

All numbers generated by the irreducible polynomial 2*n^3 - 2*n + 9 (A127989) are odd and composite. Smallest prime factor A127991, number of prime factors A127992

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A006530, A127989, A127991, A127992.

Programs

Mathematica

a = {}; Do[AppendTo[a, 2n^3 - 2n + 9], {n, 1, 300}]; b = {}; Do[c = FactorInteger[a[[n]]]; d = c[[Length[c]]]; AppendTo[b, d[[1]]], {n, 1, Length[a]}]; b

Formula

a(n) = A006530(A127989(n)). - Amiram Eldar, Mar 13 2020