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 A111091 #8 Nov 29 2017 03:41:10 %S A111091 1,3,111,313,1113111,313111313,11131113131113111, %T A111091 3131113131113111313111313,1113111313111311131311131311131113131113111 %N A111091 Successive generations of a Kolakoski(3,1) rule starting with 1 (see A066983). %C A111091 Terms are palindromic. If b_3(n) denotes the number of 3's in a(n) then b(n) satisfies the recursion: b_3(1)=0, b_3(2)=1 and b_3(n) = b_3(n-1) + b_3(n-2) + (-1)^n so that b_3(2n)=A055588(n) and b_3(2n+1)=A027941(n). If b_1(n) denotes the number of 1's: b_1(1)=1, b_1(2)=0 and b_1(n) = b_1(n-1) + b_1(n-2) - 2*(-1)^n so that b_1(2n)=A004146(n) and b_1(2n+1) = A000032(n-2) - 2. %F A111091 As n grows, a(2n-1) converges toward A095345 (read as a word) and a(2n) converges toward A095346. %e A111091 1 --> 3 --> 111 --> 313 --> 1113111 --> 313111313 %Y A111091 Cf. A111081. %K A111091 nonn %O A111091 1,2 %A A111091 _Benoit Cloitre_, Oct 12 2005