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 A217611 #10 Apr 03 2023 10:36:13
%S A217611 3,7,19,73,87211,262657,18837001,77158673929,5302306226370307681801,
%T A217611 19177458387940268116349766612211,
%U A217611 6113142872404227834840443898241613032969,328017025014102923449988663752960080886511412965881
%N A217611 Primes p such that the octal expansion of 1/p has a unique period length.
%C A217611 Also called generalized unique primes in base 8.
%H A217611 Arkadiusz Wesolowski, <a href="/A217611/b217611.txt">Table of n, a(n) for n = 1..27</a>
%H A217611 C. K. Caldwell, "Top Twenty" page, <a href="https://t5k.org/top20/page.php?id=44">Generalized Unique</a>
%H A217611 Wikipedia, <a href="http://en.wikipedia.org/wiki/Octal">Octal</a>
%t A217611 lst = {}; Do[c = Cyclotomic[n, 8]; q = c/GCD[n, c]; If[PrimePowerQ[q], p = FactorInteger[q][[1, 1]]; AppendTo[lst, p]], {n, 138}]; Sort[lst]
%Y A217611 Cf. A019326, A040017 (unique-period primes in base 10).
%K A217611 base,nonn
%O A217611 1,1
%A A217611 _Arkadiusz Wesolowski_, Oct 08 2012