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 A104158 #21 Jul 17 2025 10:13:37
%S A104158 20,5,12,9,14,11,8,16,7,19,3,17,2,15,10,6,13,4,18,1,20,5,12,9,14,11,8,
%T A104158 16,7,19,3,17,2,15,10,6,13,4,18,1,20,5,12,9,14,11,8,16,7,19,3,17,2,15,
%U A104158 10,6,13,4,18,1,20,5,12,9,14,11,8,16,7,19,3,17,2,15,10,6
%N A104158 Numbers on a standard, London, or clock dartboard read in a counterclockwise direction.
%C A104158 Sequence is periodic with period 20. - _Michel Marcus_, Jul 26 2013
%D A104158 GCHQ, The GCHQ Puzzle Book, Penguin, 2016. See page 82.
%H A104158 Paolo Xausa, <a href="/A104158/b104158.txt">Table of n, a(n) for n = 0..10000</a>
%H A104158 K. S. Brown, <a href="http://www.mathpages.com/home/kmath025.htm">The Dartboard Sequence</a>
%H A104158 Patrick Chaplin, <a href="http://web.ukonline.co.uk/patrick.chaplin/Darts_History/why_are_the_numbers_on_a_dartboa.htm">Why are the numbers on a dartboard in the order they are?</a>
%H A104158 Sven Silow, <a href="http://www.thedartmart.com/dart_faq/Sect1/14.htm">Why this particular numbering scheme?</a>
%H A104158 <a href="/index/Rec#order_20">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1).
%t A104158 PadRight[{}, 100, {20, 5, 12, 9, 14, 11, 8, 16, 7, 19, 3, 17, 2, 15, 10, 6, 13, 4, 18, 1}] (* _Paolo Xausa_, Jul 17 2025 *)
%Y A104158 Cf. A003833, A008575.
%K A104158 nonn,easy
%O A104158 0,1
%A A104158 Andrew G. West (WestA(AT)wlu.edu), Mar 09 2005