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%I #21 May 30 2021 09:01:03
%S 1,4,38,661,16286,527654,21191208,1015335608,56484795166,
%T 3576188894116,253756155257774,19937566770720487,1717714713900798962,
%U 160977153444563000938,16300053518916522372836,1773133639291617644092637,206197950879511078156507433
%N Number of ways to place n nonattacking ferses on an n X n board.
%C Fers is a leaper [1,1].
%H V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Non-attacking chess pieces</a>, 6ed, 2013, p. 423.
%F Asymptotic (Kotesovec, 2011): a(n) ~ n^(2n)/n!*exp(-5/2).
%Y Cf. A201243 - A201248, A002465, A067965.
%K nonn,hard
%O 1,2
%A _Vaclav Kotesovec_, Dec 06 2011
%E a(15) from _Vaclav Kotesovec_, Jan 03 2012
%E a(16) from _Vaclav Kotesovec_, Aug 31 2016
%E a(17) from _Vaclav Kotesovec_, May 30 2021
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