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 A042975 #15 Aug 04 2025 17:45:49
%S A042975 3,4,8,0,2,4,5,8,5,4,9,8,0,9,5,3,9,4,4,2,8,8,3,3,3,6,8,4,2,4,0,9,5,7,
%T A042975 1,9,7,2,6,4,0,7,8,7,7,2,1,2,8,6,6,2,8,1,6,0,4,5,6,3,0,3,6,4,9,7,4,4,
%U A042975 1,4,8,2,4,2,2,0,5,7,6,4,1,3,6,0,8,7,3,9,2,7,1,3,6,8,4,3,1,6,8
%N A042975 Decimal expansion of sqrt(0.121121112...).
%H A042975 Vincenzo Librandi, <a href="/A042975/b042975.txt">Table of n, a(n) for n = 0..1000</a>
%H A042975 C. V. Eynden, <a href="http://www.jstor.org/stable/2975298">Problem 10439. An irrational mimic of 1/9</a>, Amer. Math. Monthly, 104 (1997), 873.
%t A042975 With[{c=FromDigits[Flatten[Most[Riffle[Table[PadRight[{},n,1],{n,50}], 2]]]]},RealDigits[Sqrt[c/10^IntegerLength[c]],10,120][[1]]] (* _Harvey P. Dale_, Oct 12 2013 *)
%Y A042975 Cf. A042974.
%K A042975 nonn,cons
%O A042975 0,1
%A A042975 _N. J. A. Sloane_