A071216 - OEIS

%I #21 Aug 29 2019 05:05:34

%S 5,2,3,3,3,5,3,7,13,5,17,13,7,5,5,7,5,2,23,3,19,3,43,31,11,17,7,3,37,

%T 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,

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

%N a(n) is the largest prime factor of prime(n) + prime(n+1).

%H Amiram Eldar, <a href="/A071216/b071216.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A006530(A001043(n)).

%t pf[x_] := Part[Reverse[Flatten[FactorInteger[x]]],2]; Table[pf[Prime[w+1]+Prime[w]], {w,1,128}]

%o (PARI) a(n) = vecmax(factor(prime(n)+prime(n+1))[,1]); \\ _Michel Marcus_, Aug 29 2019

%Y Cf. A006530, A001043, A071215.

%K easy,nonn

%O 1,1

%A _Labos Elemer_, May 17 2002