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 A089267 #11 Apr 23 2021 11:48:37
%S A089267 0,1,1,23,1,2,1,18815,3,1,23,3,1,23,1,2,1,106597754640383,3,1,23,1,3,
%T A089267 23,1,3,18815,1,2,1,23,3,1,23,1,2,1,18815,3,1,23,3,1,23,1,2,1,
%U A089267 1715738475058821295603924428015888899408203312889855,3,1
%N A089267 Continued fraction expansion with iterated 3-fold symmetry.
%H A089267 H. Cohn, <a href="http://arXiv.org/abs/math.NT/0008221">Symmetry and specializability in continued fractions</a>
%F A089267 Sum_{k=0..infinity} 1/chebyshev(4^k, 2) = 0.51030927976262776140...
%t A089267 nmax = 50; f[m_] := ContinuedFraction[ Sum[ 1/ChebyshevT[4^k, 2], {k, 0, m}]]; A089267 = Catch[ For[m = 1, True, m++, If[ Length[fm = f[m]] > nmax, Throw[ fm[[1 ;; nmax]] ]]]] (* _Jean-François Alcover_, Sep 19 2012 *)
%o A089267 (PARI) contfrac(suminf(k=0,1/subst(poltchebi(4^k),x,2)))
%o A089267 (PARI) contfrac(suminf(k=0,1/polchebyshev(4^k,1,2))) \\ _Charles R Greathouse IV_, May 28 2015
%Y A089267 Cf. A007400.
%K A089267 nonn,cofr,nice
%O A089267 1,4
%A A089267 _Ralf Stephan_, Oct 30 2003