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 A090072 #9 Nov 30 2013 11:49:09 %S A090072 1,20000,20002,1000000,1000001,10000000,10000001 %N A090072 Numbers n such that there are (presumably) eleven palindromes in the Reverse and Add! trajectory of n. %C A090072 Additional terms (cf. A090075) are 100000000, 100000001, 100010001, 1000000000, 1000000001, 10000000000, 10000000001, 100000000000, 100000000001, 1000000000000, 1000000000001, 1000001000001, 1000100010001, but it is not yet ascertained that they are consecutive. %C A090072 For all terms given above 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 5000 steps. %C A090072 Only two numbers are known whose Reverse and Add trajectory contains twelve palindromes: 10000 and 10001. It is conjectured that these are the only such numbers and it has been conjectured before (cf. A077594) that no Reverse and Add trajectory contains more than twelve palindromes. %H A090072 <a href="/index/Res#RAA">Index entries for sequences related to Reverse and Add!</a> %e A090072 The trajectory of 1 begins 1, 2, 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 1, 2, 4, 8, 77, 1111, 2222, 4444, 8888, 661166 and 3654563 are the eleven palindromes in the trajectory of 1 and 1 is a term. %Y A090072 Cf. A023108, A023109, A065001, A070742, A077594, A090075. %K A090072 nonn,base %O A090072 1,2 %A A090072 _Klaus Brockhaus_, Nov 20 2003