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Number of ways to arrange 7 nonattacking queens on the lower triangle of an n X n board.
1

%I #8 Oct 27 2019 22:12:18

%S 0,0,0,0,0,0,0,0,0,10,1210,27198,322782,2564988,15372702,74615814,

%T 306900410,1105651074,3569169990,10512880400,28628691842,72880455042,

%U 174895586328,398556484840,867314768878,1811576604968,3646385889888

%N Number of ways to arrange 7 nonattacking queens on the lower triangle of an n X n board.

%C Column 7 of A194498.

%H R. H. Hardin, <a href="/A194497/b194497.txt">Table of n, a(n) for n = 1..28</a>

%e Some solutions for 10 X 10:

%e 0 0 0

%e 0 0 0 0 0 0

%e 0 0 0 0 0 0 0 0 0

%e 0 1 0 0 0 1 0 0 0 0 0 1

%e 0 0 0 1 0 0 0 0 1 0 1 0 0 0 0

%e 1 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0

%e 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 1 0

%e 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0

%e 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0

%e 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0

%K nonn

%O 1,10

%A _R. H. Hardin_, Aug 26 2011