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%I #2 Mar 30 2012 18:57:10
%S 0,1,1,1,2,1,2,3,3,2,2,4,4,4,2,3,5,6,6,5,3,3,6,7,8,7,6,3,4,7,9,10,10,
%T 9,7,4,4,8,10,12,12,12,10,8,4,5,9,12,14,15,15,14,12,9,5,5,10,13,16,17,
%U 18,17,16,13,10,5,6,11,15,18,20,21,21,20,18,15,11,6,6,12,16,20,22
%N Rectangular array R by antidiagonals: R(m,n) = number of black squares
%C Antidiagonal sums: (2,4,10,16,28,40,60,80,...)=A006584 (conjectured).
%C Diagonals: A007590, A000217.
%F R(m,n)=Floor(mn/2).
%e Northwest corner:
%e 0 1 1 2 2 3 3 4
%e 1 2 3 4 5 6 7 8
%e 1 3 4 6 7 9 10 12
%e 2 4 6 8 10 12 14 16
%Y Cf. A143901.
%K nonn,tabl
%O 1,5
%A _Clark Kimberling_, Sep 04 2008