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 A087001 #8 Feb 16 2025 08:32:50 %S A087001 142,9,769,58823529,526315789,43478260869,34482758620689, %T A087001 21276595744680851063829,16949152542372881355932203389, %U A087001 163934426229508196721311475409,1369,1123595505617977528089 %N A087001 Left half of periodic part of decimal expansion of 1/p for those primes having a periodic part of even length. %C A087001 a(n) = floor(A086999(n)/10^A087000(n)); A055642(a(n))=A087000(n); %C A087001 a(n) + A087002(n) = 10^A087000(n) - 1. %D A087001 H. Rademacher and O. Toeplitz, Von Zahlen und Figuren (Springer 1930, reprinted 1968), ch. 19, Die periodischen Dezimalbrueche. %H A087001 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MidysTheorem.html">Midy's Theorem</a> %H A087001 <a href="/index/1#1overn">Index entries for sequences related to decimal expansion of 1/n.</a> %e A087001 p=17: A086999(4)=5882352941176470 -> [58823529][41176470] -> %e A087001 A087001(4)=58823529, A087002(4)=41176470, %e A087001 A087001(4)+A087002(4)=58823529+41176470=99999999. %K A087001 nonn,base %O A087001 1,1 %A A087001 _Reinhard Zumkeller_, Jul 29 2003