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 A228440 #30 Feb 15 2016 04:55:59
%S A228440 1,11,121,253,1331,2783,5819,11891,14641,29161,30613,64009,130801,
%T A228440 133837,161051,273493,320771,336743,558877,640343,670703,704099,
%U A228440 895873,1438811,1472207,1771561,3008423,3078251,3528481,3544453,3704173,6147647,6290339,7027801
%N A228440 Numbers n dividing u(n), where the Lucas sequence is defined u(i) = u(i-1) - 3*u(i-2) with initial conditions u(0)=0, u(1)=1.
%C A228440 Since the absolute value of the discriminant of the characteristic polynomial is prime (=11), the sequence contains every nonnegative integer power of 11 (A001020 is subsequence). Other terms are formed on multiplication of 11^k by sporadic primes.
%H A228440 Lars Blomberg, <a href="/A228440/b228440.txt">Table of n, a(n) for n = 1..65</a>
%H A228440 C. Smyth, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL13/Smyth/smyth2.html">The Terms in Lucas Sequences Divisible by their Indices</a>, Journal of Integer Sequences, Vol.13 (2010), Article 10.2.4
%H A228440 Wikipedia, <a href="http://en.wikipedia.org/wiki/Lucas_sequence">Lucas sequence</a>
%e A228440 u(1)=1 and u(11)=253. Clearly n divides u(n) for these terms.
%t A228440 nn = 10000; s = LinearRecurrence[{1, -3}, {1, 1}, nn]; t = {}; Do[
%t A228440 If[Mod[s[[n]], n] == 0, AppendTo[t, n]], {n, nn}]; t (* _T. D. Noe_, Nov 06 2013 *)
%Y A228440 Cf. A214733 (Lucas sequence u(n) ignoring sign).
%Y A228440 Cf. A001020 (powers of 11).
%K A228440 nonn
%O A228440 1,2
%A A228440 _Thomas M. Bridge_, Nov 02 2013
%E A228440 a(27)-a(34) from _Lars Blomberg_, Feb 15 2016