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A143996 Rectangular array by antidiagonals: label each unit square in the first quadrant lattice by its northeast vertex (x,y) and mark squares for which (x,y) is congruent mod 4 to one of the following: (1,4), (2,2), (3,3), (4,1); then R(m,n) is the number of marked squares in the rectangle [0,m]x[0,n].

%I A143996 #7 Dec 06 2017 10:56:11
%S A143996 0,0,0,0,1,0,1,1,1,1,1,2,2,2,1,1,2,3,3,2,1,1,3,3,4,3,3,1,2,3,4,5,5,4,
%T A143996 3,2,2,4,5,6,6,6,5,4,2,2,4,6,7,7,7,7,6,4,2,2,5,6,8,8,9,8,8,6,5,2,3,5,
%U A143996 7,9,10,10,10,10,9,7,5,3,3,6,8,10,11,12,12,12,11,10,8,6,3,3,6,9,11,12,13,14
%N A143996 Rectangular array by antidiagonals: label each unit square in the first quadrant lattice by its northeast vertex (x,y) and mark squares for which (x,y) is congruent mod 4 to one of the following: (1,4), (2,2), (3,3), (4,1); then R(m,n) is the number of marked squares in the rectangle [0,m]x[0,n].
%C A143996 Row 4n is given by n*(1,2,3,4,5,6,...).
%H A143996 G. C. Greubel, <a href="/A143996/b143996.txt">Table of n, a(n) for the first 50 rows, flattened</a>
%F A143996 R(m,n) = floor(m*n/4).
%t A143996 b[n_, m_] := Floor[m*n/4]; a:= Table[a[n, m], {n, 1, 25}, {m, 1, 25}]; Table[a[[k, n - k + 1]], {n, 1, 20}, {k, 1, n}] // Flatten (* _G. C. Greubel_, Dec 05 2017 *)
%Y A143996 Cf. A143997, A143998, A143999, A144000, A144001.
%K A143996 nonn,tabl
%O A143996 1,12
%A A143996 _Clark Kimberling_, Sep 07 2008