%I #13 May 24 2021 01:27:05
%S 1,6,70,1289,33864,1148760,47700972,2344465830,133055587660,
%T 8559364525414,615266768106190,48861588247978827,4247584874013608724,
%U 401107335066453376830,40880928693752664368224,4472281486633326131737868
%N Number of ways to place n non-attacking semi-knights on an n x n chessboard
%C Semi-knight is a semi-leaper [1,2]. Moves of a semi-knight are allowed only in [2,1] and [-2,-1]. See also semi-bishops (A187235).
%H V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Non-attacking chess pieces</a>, 6ed, p.289
%F Asymptotic: a(n) ~ n^(2n)/n!*exp(-3/2).
%Y Cf. A182562, A201540, A201513, A002465, A201511, A197989, A201861.
%K nonn,hard,more
%O 1,2
%A _Vaclav Kotesovec_, May 05 2012
%E a(16) from _Vaclav Kotesovec_, May 24 2021