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 A384493 #19 Jun 04 2025 21:30:23
%S A384493 20,35,104,207,399,464,650,1519,1952,2015,2774,2915,2975,4454,11339,
%T A384493 22847,32318,63503,97019,122499,130304,352835,522752,924482,1949375,
%U A384493 7366463,8382464,9486399,15857855,30222023,39992975,49280399,63483104,65094623,69291935,95309054
%N A384493 Composite integers k such that sigma(k) | (k + 1)*tau(k) where tau is number of divisors of k.
%e A384493 104 is in the sequence as tau(104) = 8, sigma(104) = 210 and sigma(104) = 210 | 840 = (104 + 1) * 8 = (104 + 1) * tau(104).
%t A384493 Select[Range[4, 2^20], And[CompositeQ[#1], Divisible[(#1 + 1)*#2, #3]] & @@ Prepend[DivisorSigma[{0, 1}, #], #] &] (* _Michael De Vlieger_, May 31 2025 *)
%o A384493 (PARI) is(n) = my(f = factor(n), nd = numdiv(f)); nd > 2 && ((n+1)*nd) % sigma(f) == 0
%o A384493 (Python)
%o A384493 from sympy import divisors, isprime
%o A384493 def ok(n): return n > 3 and not isprime(n) and (n+1)*len(d:=divisors(n))%sum(d) == 0
%o A384493 print([k for k in range(10**6) if ok(k)]) # _Michael S. Branicky_, May 31 2025
%Y A384493 Composites in A384354.
%K A384493 nonn
%O A384493 1,1
%A A384493 _David A. Corneth_ and _Ivan N. Ianakiev_, May 31 2025