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 A087002 #7 Feb 16 2025 08:32:50 %S A087002 857,0,230,41176470,473684210,56521739130,65517241379310, %T A087002 78723404255319148936170,83050847457627118644067796610, %U A087002 836065573770491803278688524590,8630,8876404494382022471910 %N A087002 Right half of periodic part of decimal expansion of 1/p for those primes having a periodic part of even length. %C A087002 a(n) = A086999(n) mod 10^A087000(n); A055642(a(n))=A087000(n); %C A087002 A087001(n) + a(n) = 10^A087000(n) - 1. %D A087002 H. Rademacher and O. Toeplitz, Von Zahlen und Figuren (Springer 1930, reprinted 1968), ch. 19, Die periodischen Dezimalbrueche. %H A087002 <a href="/index/1#1overn">Index entries for sequences related to decimal expansion of 1/n.</a> %H A087002 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MidysTheorem.html">Midy's Theorem</a> %e A087002 p=19: A086999(5)=526315789473684210 -> [526315789][473684210] -> %e A087002 A087001(5)=526315789, A087002(5)=473684210, %e A087002 A087001(5)+A087002(5)=526315789+473684210=999999999. %K A087002 nonn,base %O A087002 1,1 %A A087002 _Reinhard Zumkeller_, Jul 29 2003