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 A242925 #10 Jul 04 2018 20:16:12
%S A242925 1,2,3,4,6,7,8,11,12,14,15,16,18,19,20,24,30,31,34,40,42,44,60,72,80,
%T A242925 83,130,132,136,195,208,218,232,254,258,259,260,264,272,276,305,306,
%U A242925 408,420,440,464,504,560,585,586,594,595,609,624,636,715,819,840
%N A242925 Numbers k such that lambda(k) divides Sum_{j=1..k} lambda(j).
%C A242925 Numbers k such that A162578(k)/A002322(k) = Sum_{j=1..k}A002322(j)/ A002322(k) is an integer where lambda(k) is the Carmichael lambda function (A002322).
%C A242925 The corresponding integers are 1, 2, 2, 3, 6, 3, 10, 4, 21, 10, 16, 17, 15, 6, 28, 76, 60, 9, 19, 98, ...
%H A242925 G. C. Greubel, <a href="/A242925/b242925.txt">Table of n, a(n) for n = 1..1500</a>
%e A242925 12 is in the sequence because A162578(12)/A002322(12) = 42/2 = 21 is an integer.
%p A242925 with(numtheory):nn:=2000:for n from 1 to nn do:p:=lambda(n): s:=sum('lambda(j)', 'j'=1..n):if irem(s,p)=0 then printf(`%d, `,n):else fi:od:
%t A242925 nn = 2000; sums = Accumulate[CarmichaelLambda[Range[nn]]]; Select[Range[nn], Mod[sums[[#]],CarmichaelLambda[#]] == 0 &]
%Y A242925 Cf. A194855, A002322, A162578.
%K A242925 nonn
%O A242925 1,2
%A A242925 _Michel Lagneau_, May 26 2014