A076569 Greatest prime divisor of 6n+15 (sum of six successive integers).

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, 29, 7

Offset

1,1

Comments

The greatest prime divisor (GPD) of 6n+15=3*(2n+5) is the maximum of 3 and the GPD(2n+5). Because 2n+5 is odd this is GPD(2n+5) and appart from an index shift GPD(2n+1). The GPD of 4n+6=2(2n+3) is GPD(2n+3) because 2n+3 is odd and has a GPD>=3, and apart from an index shift GPD(2n+1). This relates this sequences to A076567. - R. J. Mathar, Jul 10 2026

Links

Table of n, a(n) for n=1..71.

Formula

a(n) = A006530(6*n+15) = A006530(A016945(n+2)). - R. J. Mathar, Jul 10 2026

Mathematica

Table[FactorInteger[6n+15][[-1, 1]], {n, 80}] (* Harvey P. Dale, Aug 20 2014 *)

Crossrefs

Essentially the same as A076567.

Sequence in context: A138859 A257328 A361416 * A061194 A387122 A248280

Adjacent sequences: A076566 A076567 A076568 * A076570 A076571 A076572

Keyword

easy,nonn

Author

Zak Seidov, Oct 19 2002

Status

approved