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 A278830 #24 Dec 26 2020 06:36:47 %S A278830 20,20,31,32,46,48,52,55,61,63 %N A278830 Maximal number of possible moves at the n-th ply of a chess game. %C A278830 In view of the 75-moves rule any chess game is finite. %C A278830 The largest value appearing in the sequence is thought to be 218. - _François Labelle_, Dec 01 2016 %H A278830 A. Dickins, <a href="http://www.talkchess.com/forum/viewtopic.php?topic_view=threads&p=410026&t=39332">Record number of legal moves in a legal position</a>, 1968 %H A278830 <a href="/index/Ch#chess">OEIS index to sequences related to chess</a>. %e A278830 In the initial position of the chess game, each player has 20 possible moves (16 pawn moves and 4 knight moves), and the first (half-)move made by White does not affect the 20 possibilities Black will have thereafter. %e A278830 At its second move, i.e., ply 3 of the game, White may have as much as 31 possible moves, if White started with e2-e4 as first move, and Black offered a pawn with d7-d5 or f7-f5. %Y A278830 Cf. A278831: minimal number of possible moves at the n-th ply. %Y A278830 Cf. A278832: maximal material difference at the end of the n-th ply. %Y A278830 Cf. A083276. %K A278830 nonn,hard,more,fini %O A278830 1,1 %A A278830 _M. F. Hasler_, Nov 29 2016 %E A278830 a(3)-a(4) corrected and a(5)-a(10) from _François Labelle_, Nov 29 2016