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 A338753 #5 Feb 16 2025 08:34:00
%S A338753 0,1,0,2,3,1,0,4,2,5,0,3,1,2,4,6,0,5,0,7,3,1,0,6,8,4,0,5,0,7,0,9,2,1,
%T A338753 6,8,1,1,7,10,0,8,0,3,9,1,0,10,0,11,2,9,0,2,4,10,2,1,0,11,0,1,11,12,
%U A338753 12,5,0,3,2,13,0,12,0,3,13,3,14,15,1,13,0,1,0,16,4,1,2,6,0,14
%N A338753 Number of integers less than n with the same period of reciprocal as n.
%H A338753 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/RepeatingDecimal.html">Repeating Decimal</a>
%H A338753 <a href="/index/1#1overn">Index entries for sequences related to decimal expansion of 1/n</a>
%F A338753 a(n) = |{j < n : A051626(j) = A051626(n)}|.
%e A338753 a(14) = 2 because A051626(14) = 6 and also A051626(7) = A051626(13) = 6.
%e A338753 More specifically,
%e A338753 1/7 = 0.142857(142857)... (period 6),
%e A338753 1/13 = 0.076923(076923)... (period 6),
%e A338753 1/14 = 0.0714285(714285)... (period 6).
%t A338753 Table[Length[Select[Range[n - 1], Length[RealDigits[1/#][[1, -1]]] == Length[RealDigits[1/n][[1, -1]]] &]], {n, 90}]
%Y A338753 Cf. A051626.
%K A338753 nonn,base
%O A338753 1,4
%A A338753 _Ilya Gutkovskiy_, Nov 06 2020