OFFSET
1,1
COMMENTS
All terms are divisible by 1806. A345975 provides the terms divided by the common factor.
1806 is the only squarefree term.
LINKS
Mees de Vries, Table of n, a(n) for n = 1..126
Mees de Vries, Code for generating large instances
FORMULA
a(n) = 1806*A345975(n).
EXAMPLE
The prime divisors of 1806 are 2, 3, 7, 43. 1806 is divisible by each of 1, 2, 6, 42. The remaining even divisors of 1806 are 14, 86, 602, 1806, and none of 15, 87, 603 or 1807 are prime.
PROG
(Python)
from sympy import isprime, divisors, primefactors
def a(n): return all(n % (div + 1) == 0 for div in divisors(n) if isprime(div + 1)) and all(n % (div - 1) == 0 for div in primefactors(n))
(Python) See De Vries link.
CROSSREFS
KEYWORD
nonn
AUTHOR
Mees de Vries, Jun 26 2021
STATUS
approved