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 A180437 #30 Mar 31 2024 12:04:38 %S A180437 0,0,0,6,24,78,186,372,876,1632,3024,5310,8496,13344,21186,31878, %T A180437 46752,66936,94800,130194 %N A180437 a(n) counts the distinct cubical (on alphabet of 3 symbols) billiard words with length n, acting as prefix to just k = 1 such word of length n+1 (that is, not "special"). %C A180437 By symmetry under reversal, a(n) also counts length n cubical billiard words acting as suffix to just k length n+1 cubical billiard words. The attached program counts k-special words for k = 1,...,m, where m = 3 denotes the size of the alphabet. %H A180437 Fred Lunnon, <a href="/A180437/a180437.txt">Magma program</a> %o A180437 (Magma) // See Links. %Y A180437 Cf. A005598, A180238, A180239, A180438, A180439. %K A180437 nonn,more %O A180437 0,4 %A A180437 _Fred Lunnon_, Sep 05 2010