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A204267 Symmetric matrix: f(i,j)=(i+j+1 mod 3), by antidiagonals.

%I A204267 #8 Jan 06 2018 10:59:08
%S A204267 0,1,1,2,2,2,0,0,0,0,1,1,1,1,1,2,2,2,2,2,2,0,0,0,0,0,0,0,1,1,1,1,1,1,
%T A204267 1,1,2,2,2,2,2,2,2,2,2,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,2,2,
%U A204267 2,2,2,2,2,2,2,2,2,2,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1
%N A204267 Symmetric matrix: f(i,j)=(i+j+1 mod 3), by antidiagonals.
%C A204267 A block matrix over {0,1,2}.  See A204263 for a guide to related matrices and permanents.
%H A204267 G. C. Greubel, <a href="/A204267/b204267.txt">Table of n, a(n) for the first 100 rows, flattened</a>
%e A204267 Northwest corner:
%e A204267 0 1 2 0 1 2
%e A204267 1 2 0 1 2 0
%e A204267 2 0 1 2 0 1
%e A204267 0 1 2 0 1 2
%e A204267 1 2 0 1 2 0
%e A204267 2 0 1 2 0 1
%t A204267 f[i_, j_] := Mod[i + j + 1, 3];
%t A204267 m[n_] := Table[f[i, j], {i, 1, n}, {j, 1, n}]
%t A204267 TableForm[m[8]] (* 8x8 principal submatrix *)
%t A204267 Flatten[Table[f[i, n + 1 - i],
%t A204267   {n, 1, 14}, {i, 1, n}]]    (* A204267 *)
%t A204267 Permanent[m_] :=
%t A204267   With[{a = Array[x, Length[m]]},
%t A204267    Coefficient[Times @@ (m.a), Times @@ a]];
%t A204267 Table[Permanent[m[n]], {n, 1, 22}]  (* A204268 *)
%Y A204267 Cf. A204268.
%K A204267 nonn,tabl
%O A204267 1,4
%A A204267 _Clark Kimberling_, Jan 15 2012