A284671 Numbers n > 2 such that A258409(n)*A002322(n) divides n-1.

1729, 41041, 75361, 172081, 449065, 656601, 670033, 1050985, 2433601, 2704801, 3664585, 4903921, 6840001, 7995169, 8355841, 8719921, 9582145, 9613297, 9890881, 10402561, 11205601, 12945745, 13992265, 15888313, 16778881, 17586361, 17812081, 19683001, 20964961

Offset: 1

Author

Thomas Ordowski and Altug Alkan, Apr 01 2017

Keywords

• nonn

Comments

A proper subset of the Carmichael numbers A002997.

If n is in the sequence, then n-1 is not squarefree.

Problem: are there infinitely many such numbers?

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A002322, A002997, A258409.

Programs

Mathematica

Select[Range[3, 10^6], Divisible[#-1, CarmichaelLambda[#] * GCD @@ (Divisors[#] - 1)]  &] (* Amiram Eldar, Jun 26 2019 *)