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%I #38 Dec 04 2022 15:58:41
%S 1,4,25,121,568,2144,8231,27473,92244,279241,831581,2284733,6118941,
%T 15465573,37720667,88273017,197300906,429114775,881951878,1784140720,
%U 3373100313,6336692489,11005448210,19131647821,30415473928,48633111249
%N Number of positions in game "Connect Four" (played on usual 6-row, 7-column board) after n moves, up to reflection.
%H Sean A. Irvine, <a href="/A013582/b013582.txt">Table of n, a(n) for n = 0..42</a> [a(42) corrected by Sidney Cadot]
%H John Tromp, <a href="http://tromp.github.io/c4/c4.html">John's Connect Four Playground</a>, viewed Jan 23 2014.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Connect-Four.html">Connect-Four</a>
%Y Cf. A212693.
%K nonn,fini,full
%O 0,2
%A _Russ Cox_
%E Name clarified by _Charles R Greathouse IV_, Dec 01 2013
%E a(3)-a(13) corrected by _Sean A. Irvine_, Aug 09 2018. The corrected values were confirmed by _Russ Cox_ and extended through a(15), Aug 13 2018
%E a(16)-a(17) from _Sean A. Irvine_, Aug 15 2018
%E Remaining terms a(18)-a(42) from _Sean A. Irvine_, Oct 02 2018
%E a(42) corrected by _Sidney Cadot_, Dec 04 2022, after comparing results of an independent solver and confirming with _Sean A. Irvine_ that the previously given value was indeed erroneous.
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