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 A331542 #15 Jan 25 2020 09:21:57 %S A331542 1,8,0,2,6,1,7,4,9,9,7,8,5,2,5,4,1,1,5,9,6,2,7,7,7,3,8,0,1,0,0,2,1,4, %T A331542 7,4,5,8,8,4,0,3,7,2,2,2,6,1,9,8,9,9,7,8,5,2,5,4,1,1,5,9,6,2,7,7,7,3, %U A331542 8,0,1,0,0,2,1,4,7,4,5,8,8,4,0,3,7,2,2,2,6,1,9,8 %N A331542 The speed of light in furlongs per fortnight. %C A331542 Arguably the most well known FFF constant. Note that its precise value depends on the definition of the furlong being used. The value given here is using the international definition of the inch which equals 25.4 millimeters, thus one furlong equals 201.168 meters precisely. %C A331542 From _Jianing Song_, Jan 25 2020: (Start) %C A331542 Decimal expansion of 2518256647200000/1397. %C A331542 Period 42: repeat [9, 9, 7, 8, 5, 2, 5, 4, 1, 1, 5, 9, 6, 2, 7, 7, 7, 3, 8, 0, 1, 0, 0, 2, 1, 4, 7, 4, 5, 8, 8, 4, 0, 3, 7, 2, 2, 2, 6, 1, 9, 8] since a(21). (End) %H A331542 Wikipedia, <a href="https://en.wikipedia.org/wiki/FFF_system">FFF System</a>, <a href="https://en.wikipedia.org/wiki/Speed_of_light">Speed of light</a>, <a href="https://en.wikipedia.org/wiki/Furlong">Furlong</a>, <a href="https://en.wikipedia.org/wiki/Fortnight">Fortnight</a>. %F A331542 1802617499785.2541159627773801002... furlongs/fortnight = (speed of light in meters/second) * (meter-to-furlong conversion) * (seconds/fortnight) = (299792458 meters/second) * (1/201.168 furlongs/meter) * (1209600 seconds/fortnight). %F A331542 a(n) = 9 - a(n-21) for n >= 42. - _Jianing Song_, Jan 25 2020 %Y A331542 Cf. A003678, A001356. %K A331542 nonn,cons,less,dumb %O A331542 13,2 %A A331542 _Scott R. Shannon_, Jan 19 2020 %E A331542 More terms from _Jianing Song_, Jan 25 2020