A076559 - OEIS

%I #12 May 10 2023 08:31:04

%S 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,

%T 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,

%U 19,5,137,31,47,3,5,103,13,7,3,167,19,29,13,89,11,37,47,127,193,131,19

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

%H Amiram Eldar, <a href="/A076559/b076559.txt">Table of n, a(n) for n = 2..10000</a>

%F a(n) = A006530(A024675(n-1)). - _R. J. Mathar_, May 10 2023

%p A076559 := proc(n)

%p     A006530((ithprime(n)+ithprime(n+1))/2) ;

%p end proc:

%p seq(A076559(n),n=2..120) ;  # _R. J. Mathar_, May 10 2023

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

%Y Cf. A071216.

%K easy,nonn

%O 2,1

%A _Zak Seidov_, Oct 19 2002