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 A023899 #23 Jul 02 2022 01:56:56
%S A023899 1,3,5,7,4,9,12,11,20,9,13,28,7,27,10,26,15,36,21,45,14,25,17,44,25,
%T A023899 35,63,8,42,42,16,19,7,52,6,49,81,24,10,30,40,70,78,21,21,19,60,18,63,
%U A023899 99,40,30,98,7,18,75,15,23,57,35,30,57,68,75,36,35,30,77,55,74,91,117
%N A023899 Integer values of divisor balance: Sum_{d divides k} {d / phi(d)} for numbers k in A023898.
%H A023899 Amiram Eldar, <a href="/A023899/b023899.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Vincenzo Librandi)
%F A023899 Divisor balance of n = Sum_{d divides n} {d / phi(d)} where phi is Euler's phi function.
%e A023899 a(9) = 20 because the 9th integer having an integer divisor balance is 36 : its divisors are 1,2,3,4,6,9,12,18 and 36, giving the fractions (1, 2, 3/2, 2, 3, 3/2, 3, 3, 3) which sum to 20.
%t A023899 Select[ Array[ Function[ n, Plus @@ Map[ #/EulerPhi[ # ]&, Divisors[ n ] ] ], 3000 ], IntegerQ ]
%t A023899 s[n_] := DivisorSum[n, #/EulerPhi[#] &]; Select[s /@ Range[4000], IntegerQ] (* _Amiram Eldar_, Jul 01 2022 *)
%Y A023899 cf. A023898 (integers for which the divisor balance is an integer).
%Y A023899 cf. A000010, A239886, A239887 for a version with proper divisors.
%K A023899 nonn
%O A023899 1,2
%A A023899 _Olivier Gérard_