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 A119761 #14 Jan 17 2019 13:44:08 %S A119761 2,3,4,6,9,10,12,14,18,19,23,24,36,38,39,46,48,62,78,93,96,106,120, %T A119761 134,150,186,196,240,268,294,300,317,320 %N A119761 Values n such that the largest prime factor of repunit R_n=(10^n -1)/9 is a unique prime,i.e.,whose reciprocal has unique decimal period length. %H A119761 M. Kamada, <a href="https://stdkmd.net/nrr/repunit/">Factorization of 11...11(Repunits)</a> %e A119761 18 is in the sequence because R_18=3^2*7*11*13*19*37*52579*333667 and 333667 is the only prime with period 9: 1/333667 =0.000002997000002997... %Y A119761 Cf. A002275, A003020, A007498, A040017. %K A119761 more,nonn,base %O A119761 1,1 %A A119761 _Lekraj Beedassy_, Jun 18 2006 %E A119761 Corrected and extended by _Hans Havermann_, Jun 22 2006 %E A119761 a(25)-a(33) from _Ray Chandler_, May 09 2017