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 A317955 #12 Aug 22 2018 02:32:45 %S A317955 1,12,1213,12131214,121312141213121,12131214121312112131214121312, %T A317955 12131214121312112131214121312121312141213121121312141213 %N A317955 Apply the morphism 1 -> 12, 2 -> 13, 3 -> 14, 4 -> 1 n times to 1, and concatenate the resulting string. %C A317955 a(n) is the concatenation a(n) = a(n-1).a(n-2).a(n-3).a(n-4) for n >= 5. %H A317955 Seiichi Manyama, <a href="/A317955/b317955.txt">Table of n, a(n) for n = 1..11</a> %Y A317955 Cf. A317953, A317954. %K A317955 nonn %O A317955 1,2 %A A317955 _N. J. A. Sloane_ and _Doron Zeilberger_, Aug 21 2018