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 A346909 #14 Oct 16 2023 01:48:45
%S A346909 3,3,3,30,330,303000,33003300000,3030000030300000000000,
%T A346909 3300330000000000330033000000000000000000000,
%U A346909 30300000303000000000000000000000303000003030000000000000000000000000000000000000000000
%N A346909 Continued fraction expansion of the constant whose decimal expansion is A269707.
%C A346909 The next term has 171 digits and is too large to include in the Data section.
%D A346909 André Blanchard and Michel Mendès France, Symétrie et transcendance, Bull. Sc. Math., 2nd series, Vol. 106 (1982), pp. 325-335.
%H A346909 Amiram Eldar, <a href="/A346909/b346909.txt">Table of n, a(n) for n = 1..13</a>
%H A346909 M. Mendes France and A. J. van der Poorten, <a href="https://doi.org/10.1112/S0025579300006380">Some explicit continued fraction expansions</a>, Mathematika, Vol. 38, No. 1 (1991), pp. 1-9.
%F A346909 a(n) = 3 * 10^((4^((n-3)/2)-1)/3) * Product_{k=0..(n-5)/2} (1 + 10^(4^k)), if n > 2 is odd, and 3 * 10^((2*4^(n/2-2)+1)/3) * Product_{k=0..n/2-3} (1 + 10^(2*4^k)), if n > 2 is even.
%e A346909 3 + 1/(3 + 1/(3 + 1/(30 + 1/(330 + ... )))) = 3.30033000000000033... (A269707).
%t A346909 a[1] = a[2] = 3; a[n_] := 3 * If[OddQ[n], 10^((4^((n - 3)/2) - 1)/3) * Product[1 + 10^(4^k), {k, 0, (n - 5)/2}], 10^((2*4^(n/2 - 2) + 1)/3) * Product[1 + 10^(2*4^k), {k, 0, n/2 - 3}]]; Array[a, 10]
%Y A346909 Cf. A269707.
%K A346909 nonn,cofr,base
%O A346909 1,1
%A A346909 _Amiram Eldar_, Aug 06 2021