login
Greatest prime divisor of prime(n) - 3.
2

%I #17 Dec 29 2015 03:03:43

%S 2,2,2,5,7,2,5,13,7,17,19,5,11,5,7,29,2,17,7,19,5,43,47,7,5,13,53,11,

%T 31,2,67,17,73,37,11,5,41,17,11,89,47,19,97,7,13,11,7,113,23,59,17,31,

%U 127,13,19,67,137,139,7,29,19,11,31,157,41,167,43,173,7,89

%N Greatest prime divisor of prime(n) - 3.

%C a(n) = 2 if prime(n) is in A057733. - _Robert Israel_, Dec 28 2015

%H Robert Israel, <a href="/A023569/b023569.txt">Table of n, a(n) for n = 3..10000</a>

%p seq(max(numtheory:-factorset(ithprime(i)-3)), i=3..100); # _Robert Israel_, Dec 28 2015

%t Table[FactorInteger[Prime[n] - 3] [[-1, 1]], {n, 3, 100}] (* _Vincenzo Librandi_, Dec 29 2015 *)

%o (PARI) a(n) = vecmax(factor(prime(n)-3)[,1]); \\ _Michel Marcus_, Dec 29 2015

%Y Cf. A023568, A057733.

%K nonn

%O 3,1

%A _Clark Kimberling_

%E Corrected by _Robert Israel_, Dec 29 2015