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 A064611 #23 Mar 17 2019 08:40:39
%S A064611 1,2,8,11,12,174,212,524,1567,14096,19795,38466,42114,55575,338809,
%T A064611 498001,1175281,2424880,3994532,7908519,48453784,696840720,5497869355,
%U A064611 7479239685
%N A064611 Partial sum of usigma is divisible by n, where usigma(n) = A034448(n) and summatory-usigma(n) = A064609(n).
%C A064611 Analogous sequences for various arithmetical functions are A050226, A056550, A064605-A064607, A064610, A064612, A048290, A062982, A045345.
%H A064611 Amiram Eldar, <a href="/A064611/a064611.txt">Table of n, a(n), A064609(a(n))/a(n) for n=1..24.</a>
%F A064611 A064609(n) mod n = 0.
%e A064611 udivisor sums[=usigma(j) values] from 1 to 8 are added: 1+3+4+5+6+12+8+9=48; it is divisible by 8, thus 8 is here.
%t A064611 s = Table[DivisorSum[n, # &, CoprimeQ[#, n/#] &], {n, 10^6}]; Module[{a = First@ s, b = {First@ s}}, Do[a += s[[i]]; If[Divisible[a, i], AppendTo[b, i]], {i, 2, Length@ s}]; b] (* _Michael De Vlieger_, Mar 18 2017 *)
%Y A064611 Cf. A034448, A064609, A050226, A056550, A064605, A064606, A064607, A064610, A064612, A048290, A062982, A045345.
%K A064611 nonn,more
%O A064611 1,2
%A A064611 _Labos Elemer_, Sep 24 2001
%E A064611 a(17)-a(22) from _Donovan Johnson_, Jul 20 2012
%E A064611 a(23)-a(24) from _Amiram Eldar_, Mar 17 2019