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%I #21 May 11 2017 17:46:08
%S 1,1,0,8,79,1974,62266,2484382,119138166,6655170642,423677826986,
%T 30242576462856,2390359529372724,207127434998494421,
%U 19516867860507198208,1986288643031862123264,217094567491104327256049,25357029929230564723578520,3151672341378566296926684684
%N Number of ways to place n nonattacking kings on an n X n board.
%H Alois P. Heinz, <a href="/A201513/b201513.txt">Table of n, a(n) for n = 0..21</a> (terms n=1..20 from Andrew Woods)
%H V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Non-attacking chess pieces</a>, 6ed, 2013, p. 77.
%F Asymptotics (Vaclav Kotesovec, Nov 29 2011): n^(2n)/n!*exp(-9/2).
%Y Cf. A061995, A061996, A061997, A061998, A172158, A194788, A201369.
%Y Cf. A063443.
%Y Main diagonal of A098487, A193580.
%K nonn,nice
%O 0,4
%A _Vaclav Kotesovec_, Dec 02 2011
%E a(0)=1 prepended by _Alois P. Heinz_, May 11 2017
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