A076567 Greatest prime divisor of 4n+6 (sum of four successive integers).

5, 7, 3, 11, 13, 5, 17, 19, 7, 23, 5, 3, 29, 31, 11, 7, 37, 13, 41, 43, 5, 47, 7, 17, 53, 11, 19, 59, 61, 7, 13, 67, 23, 71, 73, 5, 11, 79, 3, 83, 17, 29, 89, 13, 31, 19, 97, 11, 101, 103, 7, 107, 109, 37, 113, 23, 13, 17, 11, 41, 5, 127, 43, 131, 19, 5, 137, 139, 47, 13

Offset: 1

Author

Zak Seidov, Oct 19 2002

Keywords

• easy
• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A006530, A076565.

Programs

Maple

f:= n -> max(numtheory:-factorset(n)):
map(f, [seq(i,i=10..1000,4)]); # Robert Israel, Nov 10 2020

Mathematica

FactorInteger[#][[-1,1]]&/@(4*Range[70]+6) (* Harvey P. Dale, Mar 12 2017 *)

PARI

a(n) = {f = factor(4*n+6); return (f[length(f~), 1]);} \\ Michel Marcus, Apr 19 2013

PARI

a(n) = vecmax(factor(4*n+6)[,1]); \\ Michel Marcus, Nov 10 2020

Formula

a(n) = A076565(n+1) = A006530(4n+6). - R. J. Mathar, Jul 31 2008