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 A118519 #8 Jul 18 2015 11:21:31
%S A118519 3,6,9,12,24,45,57,78,90,12,24,45,57,78,90,12,24,45,57,78,90,12,24,45,
%T A118519 57,78,90,12,24,45,57,78,90,12,24,45,57,78,90,12,24,45,57,78,90,12,24,
%U A118519 45,57,78,90,12,24,45,57,78,90,12,24,45,57,78,90,12,24,45,57,78,90
%N A118519 Define sequence S_m by: initial term = m, reverse digits and add 3 to get next term. Entry shows S_3. This reaches a cycle of length 6 in 3 steps.
%H A118519 N. J. A. Sloane and others, <a href="/wiki/Sequences_of_RADD_type">Sequences of RADD type</a>, OEIS wiki.
%H A118519 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 1).
%t A118519 Join[{3,6,9},LinearRecurrence[{0,0,0,0,0,1},{12,24,45,57,78,90},66]] (* _Ray Chandler_, Jul 18 2015 *)
%Y A118519 Cf. A117831, A118517 on.
%K A118519 nonn,base
%O A118519 1,1
%A A118519 _N. J. A. Sloane_, May 06 2006