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 A090070 #9 Nov 30 2013 11:48:53 %S A090070 4,10,11,535,1000,1001,10007,10101,20006,30005,50003,60002,70001, %T A090070 80000,80008,100070,110060,120050,130040,140030,150020,160010,170000, %U A090070 170071,200000,200002,1000003,1000150,1001001,1010050,1100140,1110040,1200130 %N A090070 Numbers n such that there are (presumably) nine palindromes in the Reverse and Add! trajectory of n. %C A090070 For terms < 5000000 each palindrome is reached from the preceding one or from the start in at most 35 steps; after the presumably last one no further palindrome is reached in 2000 steps. %H A090070 <a href="/index/Res#RAA">Index entries for sequences related to Reverse and Add!</a> %e A090070 The trajectory of 4 begins 4, 8, 16, 77, 154, 605, 1111, 2222, 4444, 8888, 17776, 85547, 160105, 661166, 1322332, 3654563, 7309126, ...; at 7309126 it joins the (presumably) palindrome-free trajectory of A063048(7) = 10577, hence 4, 8, 77, 1111, 2222, 4444, 8888, 661166 and 3654563 are the nine palindromes in the trajectory of 4 and 4 is a term. %Y A090070 Cf. A023108, A023109, A065001, A070742, A077594. %K A090070 nonn,base %O A090070 1,1 %A A090070 _Klaus Brockhaus_, Nov 20 2003