A387416 Numbers k for which A003961(k) - sigma(k) is a multiple of k, where A003961 is fully multiplicative with a(prime(i)) = prime(i+1), and sigma is the sum of divisors function.

1, 2, 18, 3528

Offset: 1

Author

Antti Karttunen, Sep 03 2025

Keywords

• nonn
• more
• new

Comments

If it exists, a(5) > 3288334336.

Examples

			1 is included as A003961(1) - A000203(1) = 0 is a multiple of 1.
2 is included as A003961(2) - A000203(2) = 0 is a multiple of 2.
18 is included as A003961(18) - A000203(18) = 75 - 39 = 36 = 2 * 18.
3528 is included as A003961(3528) - A000203(3528) = 81675 - 11115 = 70560 = 20 * 3528.
		

Links

• Index entries for sequences computed from indices in prime factorization
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A003961, A286385.

Cf. also A378980.

Formula

{k | A286385(k) == 0 (mod k)}.