This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A387416 #9 Sep 04 2025 14:53:59
%S A387416 1,2,18,3528
%N 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.
%C A387416 If it exists, a(5) > 3288334336.
%H A387416 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%H A387416 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F A387416 {k | A286385(k) == 0 (mod k)}.
%e A387416 1 is included as A003961(1) - A000203(1) = 0 is a multiple of 1.
%e A387416 2 is included as A003961(2) - A000203(2) = 0 is a multiple of 2.
%e A387416 18 is included as A003961(18) - A000203(18) = 75 - 39 = 36 = 2 * 18.
%e A387416 3528 is included as A003961(3528) - A000203(3528) = 81675 - 11115 = 70560 = 20 * 3528.
%Y A387416 Cf. A000203, A003961, A286385.
%Y A387416 Cf. also A378980.
%K A387416 nonn,more,new
%O A387416 1,2
%A A387416 _Antti Karttunen_, Sep 03 2025