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 A117521 #7 Jul 19 2015 17:57:16 %S A117521 1,3,5,7,9,11,13,33,35,55,57,77,79,99,101,103,303,305,505,507,707,709, %T A117521 909,911,121,123,323,325,525,527,727,729,929,931,141,143,343,345,545, %U A117521 547,747,749,949,951,161,163,363,365,565,567,767,769,969,971,181,183,383,385,585,587,787,789,989,991,201,104,403,306,605,508,807,710,19,93,41,16,63,38,85,60,8,10,3,5,7,9,11,13,33,35,55,57,77,79,99,101,103,303,305,505,507,707 %N A117521 Start with 1 and repeatedly reverse the digits and add 2 to get the next term. %H A117521 N. J. A. Sloane and others, <a href="/wiki/Sequences_of_RADD_type">Sequences of RADD type</a>, OEIS wiki. %H A117521 <a href="/index/Rec#order_81">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1). %F A117521 After 1 step enters a cycle of length 81. %Y A117521 Cf. A117831, A118514. %K A117521 nonn,base %O A117521 1,2 %A A117521 _N. J. A. Sloane_, following discussions with Luc Stevens, May 04 2006