A023576 Greatest prime divisor of prime(n)+3.

5, 3, 2, 5, 7, 2, 5, 11, 13, 2, 17, 5, 11, 23, 5, 7, 31, 2, 7, 37, 19, 41, 43, 23, 5, 13, 53, 11, 7, 29, 13, 67, 7, 71, 19, 11, 5, 83, 17, 11, 13, 23, 97, 7, 5, 101, 107, 113, 23, 29, 59, 11, 61, 127, 13, 19, 17, 137, 7, 71, 13, 37, 31, 157, 79, 5, 167, 17, 7, 11, 89

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A006530, A113935.

Programs

Mathematica

FactorInteger[#][[-1, 1]] & /@ (Prime[Range[100]] + 3) (* Harvey P. Dale, Sep 05 2014 *)

Python

from sympy import primefactors, prime
def a(n): return primefactors(prime(n) + 3)[-1]
print([a(n) for n in range(1, 72)]) # Michael S. Branicky, May 03 2021

Formula

a(n) = A006530(A113935(n)). - Michel Marcus, May 04 2021