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 A109884 #13 Aug 17 2017 22:40:01
%S A109884 1,2,4,6,8,10,12,16,18,24,28,30,32,40,44,48,60,64,72,84,120,126,128,
%T A109884 136,140,150,152,180,184,204,216,224,234,256,270,360,420,440,462,468,
%U A109884 496,512,520,528,546,672,700,750,752,864,870,884
%N A109884 Indices k of members of A109883 such that A109883(k) is a divisor of k. Also k is a term if A109883(k) = 0.
%C A109884 2^n is a term for all n. All perfect numbers are terms.
%H A109884 Nathaniel Johnston, <a href="/A109884/b109884.txt">Table of n, a(n) for n = 1..463</a>
%e A109884 18 is a term as A109883(18) = 6, 6 is a divisor of 18.
%e A109884 6 is a term as A109883(6) = 0.
%p A109884 for n from 1 to 900 do if(A109883(n)=0 or type(n/A109883(n),integer))then print(n);fi:od: # _Nathaniel Johnston_, Apr 15 2011
%t A109884 With[{s = Table[Catch@ Fold[If[#1 < #2, Throw[#1], #1 - #2] &, n, Divisors@ n], {n, 10^3}]}, Select[MapIndexed[{First@ #2, #1 /. 0 -> 1} &, s], Divisible[#1, #2] & @@ # &][[All, 1]]] (* _Michael De Vlieger_, Aug 17 2017, after Bobby R. Treat at A109883 *)
%Y A109884 Cf. A064510, A109883.
%K A109884 easy,nonn
%O A109884 1,2
%A A109884 _Amarnath Murthy_, Jul 11 2005
%E A109884 Offset, a(11), and a(12) corrected by, and a(13) - a(52) from _Nathaniel Johnston_, Apr 15 2011