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 A002187 M0025 N0007 #27 Jul 06 2020 16:55:26 %S A002187 0,1,1,2,0,3,1,1,0,3,3,2,2,4,0,5,2,2,3,3,0,1,1,3,0,2,1,1,0,4,5,2,7,4, %T A002187 0,1,1,2,0,3,1,1,0,3,3,2,2,4,4,5,5,2,3,3,0,1,1,3,0,2,1,1,0,4,5,3,7,4, %U A002187 8,1,1,2,0,3,1,1,0,3,3,2,2,4,4,5,5,9,3,3,0,1,1,3,0,2,1,1,0,4,5,3,7,4,8,1,1,2,0,3,1,1,0,3,3,2,2,4,4,5,5,9,3,3,0,1,1,3,0,2,1,1,0,4 %N A002187 Sprague-Grundy values for Dawson's Chess (octal game .137). %C A002187 Octal game .07 (Dawson's Kayles) has values a(n-1). Octal games .4, .401, .402, .403, .42, .421, .422 and .423 have values a(n-2). %D A002187 E. R. Berlekamp, J. H. Conway and R. K. Guy, Winning Ways, Academic Press, NY, 2 vols., 1982, see pp. 89 and 102. %D A002187 R. K. Guy and C. A. B. Smith, The G-values of various games. Proc. Cambridge Philos. Soc. 52 (1956), 514-526. %D A002187 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). %D A002187 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A002187 Reinhard Zumkeller, <a href="/A002187/b002187.txt">Table of n, a(n) for n = 0..1000</a> %H A002187 Pratik Alladi, Neel Bhalla, Tanya Khovanova, Nathan Sheffield, Eddie Song, William Sun, Andrew The, Alan Wang, Naor Wiesel, Kevin Zhang Kevin Zhao, <a href="https://arxiv.org/abs/1707.07201">PRIMES STEP Plays Games</a>, arXiv:1707.07201 [math.CO], 2017, Section 8. %H A002187 Sierra Brown, Spencer Daugherty, Eugene Fiorini, Barbara Maldonado, Diego Manzano-Ruiz, Sean Rainville, Riley Waechter, and Tony W. H. Wong, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL23/Wong/wong24.html">Nimber Sequences of Node-Kayles Games</a>, J. Int. Seq., Vol. 23 (2020), Article 20.3.5. %H A002187 Achim Flammenkamp, <a href="http://www.uni-bielefeld.de/~achim/octal_sparse.html">Octal games</a> %H A002187 R. K. Guy, <a href="/A005251/a005251_1.pdf">Anyone for Twopins?</a>, in D. A. Klarner, editor, The Mathematical Gardner. Prindle, Weber and Schmidt, Boston, 1981, pp. 2-15. [Annotated scanned copy, with permission] %F A002187 Has period 34 with the only exceptions at n=0, 14, 16, 17, 31, 34 and 51. %o A002187 (Haskell) %o A002187 a002187 n = a002187_list !! n %o A002187 a002187_list = tail g where %o A002187 g = 0 : 0 : [mex [xor (g !! (a + 1)) (g !! (n - a - 2)) | %o A002187 a <- [-1 .. n - 2]] | n <- [1 ..]] %o A002187 xor 0 0 = 0 %o A002187 xor x y = let ((q,r), (s,t)) = (divMod x 2, divMod y 2) %o A002187 in (if r == t then 0 else 1) + 2 * xor q s %o A002187 mex xs = head [x | x <- [0..], not (elem x xs)] %o A002187 -- Paul Stoeber (pstoeber(AT)uni-potsdam.de), Oct 08 2005; edited by _Reinhard Zumkeller_, Dec 16 2013 %K A002187 nonn,nice,easy %O A002187 0,4 %A A002187 _N. J. A. Sloane_ %E A002187 Edited by _Christian G. Bower_, Oct 22 2002