A023569 Greatest prime divisor of prime(n) - 3.

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, 31, 2, 67, 17, 73, 37, 11, 5, 41, 17, 11, 89, 47, 19, 97, 7, 13, 11, 7, 113, 23, 59, 17, 31, 127, 13, 19, 67, 137, 139, 7, 29, 19, 11, 31, 157, 41, 167, 43, 173, 7, 89

Offset: 3

Author

Clark Kimberling

Keywords

• nonn

Comments

a(n) = 2 if prime(n) is in A057733. - Robert Israel, Dec 28 2015

Links

• Robert Israel, Table of n, a(n) for n = 3..10000

Crossrefs

Cf. A023568, A057733.

Programs

Maple

seq(max(numtheory:-factorset(ithprime(i)-3)), i=3..100); # Robert Israel, Dec 28 2015

Mathematica

Table[FactorInteger[Prime[n] - 3] [[-1, 1]], {n, 3, 100}] (* Vincenzo Librandi, Dec 29 2015 *)

PARI

a(n) = vecmax(factor(prime(n)-3)[,1]); \\ Michel Marcus, Dec 29 2015

Extensions

Corrected by Robert Israel, Dec 29 2015