A023580 Sum of distinct prime divisors of prime(n)+3.

5, 5, 2, 7, 9, 2, 7, 13, 15, 2, 19, 7, 13, 25, 7, 9, 33, 2, 14, 39, 21, 43, 45, 25, 7, 15, 55, 18, 9, 31, 20, 69, 14, 73, 21, 20, 7, 85, 24, 13, 22, 25, 99, 9, 7, 103, 109, 115, 30, 31, 61, 13, 63, 129, 20, 28, 19, 139, 14, 73, 26, 39, 38, 159, 81, 7, 169, 24, 14

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Crossrefs

Cf. A008472, A113935.

Programs

Mathematica

Total[First/@FactorInteger[#]]&/@(Prime@Range@100+3) (* Giorgos Kalogeropoulos, May 05 2021 *)

Python

from sympy import primefactors, prime
def a(n): return sum(primefactors(prime(n) + 3))
print([a(n) for n in range(1, 70)]) # Michael S. Branicky, May 05 2021

Formula

a(n) = A008472(A113935(n)). - Michel Marcus, May 05 2021