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%I #18 Jul 30 2024 17:56:29
%S 9,15,23,30,37,44,52,60,68,76,84,92,100,108,116,124,132,140,148,156,
%T 164,172,180,188,196,204,212,220,228,236,244,252,260,268,276,284,292,
%U 300,308,316,324,332,340,348,356,364,372,380,388,396,404,412,420
%N Maximum number of squares covered (i.e., attacked) by 2 independent (i.e., non-attacking) queens on an n X n chessboard.
%C It is not possible to place two non-attacking queens on a 1 X 1 or 2 X 2 chessboard.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F a(n) = 8*n - 20 for n >= 8.
%F G.f.: x^3*(9 - 3*x + 2*x^2 - x^3 + x^6)/(1 - x)^2. - _Stefano Spezia_, Jul 25 2024
%Y Cf. A017113, A047461 (case for one queen).
%K nonn,easy
%O 3,1
%A _John King_, Jul 24 2024