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%I A194487 #10 May 05 2018 08:07:57
%S A194487 0,1,12,62,253,804,2136,4958,10376,20013,36144,61846,101163,159286,
%T A194487 242748,359634,519806,735143,1019796,1390458,1866649,2471016,3229648,
%U A194487 4172406,5333268,6750689,8467976,10533678,13001991,15933178,19394004
%N A194487 Number of ways to arrange 3 nonattacking knights on the lower triangle of an n X n board.
%C A194487 Column 3 of A194492.
%H A194487 R. H. Hardin, <a href="/A194487/b194487.txt">Table of n, a(n) for n = 1..200</a>
%F A194487 Empirical: a(n) = (1/48)*n^6 + (1/16)*n^5 - (17/16)*n^4 + (133/48)*n^3 + (433/24)*n^2 - (743/6)*n + 218 for n>4.
%F A194487 Empirical g.f.: x^2*(1 + 5*x - x^2 + 36*x^3 - 50*x^4 + 50*x^5 - 40*x^6 + 22*x^7 - 12*x^8 + 4*x^9) / (1 - x)^7. - _Colin Barker_, May 05 2018
%e A194487 Some solutions for 3 X 3:
%e A194487 ..1......0......1......1......0......0......1......0......0......0......1
%e A194487 ..0.1....1.1....1.1....1.0....0.1....0.1....0.1....1.0....1.1....0.0....0.0
%e A194487 ..1.0.0..1.0.0..0.0.0..1.0.0..0.1.1..1.0.1..0.0.1..1.1.0..0.1.0..1.1.1..1.0.1
%Y A194487 Cf. A194492.
%K A194487 nonn
%O A194487 1,3
%A A194487 _R. H. Hardin_, Aug 26 2011

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