A076559 Greatest prime divisor of n-th interprime: (prime(n) + prime(n+1))/2.

2, 3, 3, 3, 5, 3, 7, 13, 5, 17, 13, 7, 5, 5, 7, 5, 2, 23, 3, 19, 3, 43, 31, 11, 17, 7, 3, 37, 5, 43, 67, 23, 3, 5, 11, 5, 11, 17, 11, 5, 31, 3, 13, 11, 41, 31, 5, 19, 11, 59, 5, 41, 127, 13, 19, 5, 137, 31, 47, 3, 5, 103, 13, 7, 3, 167, 19, 29, 13, 89, 11, 37, 47, 127, 193, 131, 19

Offset: 2

Author

Zak Seidov, Oct 19 2002

Keywords

• easy
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 2..10000

Crossrefs

Cf. A071216.

Programs

Maple

A076559 := proc(n)
    A006530((ithprime(n)+ithprime(n+1))/2) ;
end proc:
seq(A076559(n),n=2..120) ;  # R. J. Mathar, May 10 2023

Mathematica

gpf[n_] := FactorInteger[n][[-1, 1]]; p = Select[Range[405], PrimeQ]; gpf /@ ((p[[2 ;; -2]] + p[[3 ;; -1]])/2) (* Amiram Eldar, Aug 29 2019 *)

Formula

a(n) = A006530(A024675(n-1)). - R. J. Mathar, May 10 2023