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A204421 Symmetric matrix: f(i,j)=(i+j+2 mod 3), by antidiagonals.

%I A204421 #10 Mar 30 2012 18:58:08
%S A204421 1,2,2,0,0,0,1,1,1,1,2,2,2,2,2,0,0,0,0,0,0,1,1,1,1,1,1,1,2,2,2,2,2,2,
%T A204421 2,2,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,2,0,0,
%U A204421 0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2
%N A204421 Symmetric matrix: f(i,j)=(i+j+2 mod 3), by antidiagonals.
%C A204421 A block matrix over {0,1,2}.  See A204263 for a guide to related matrices and permanents.
%e A204421 Northwest corner:
%e A204421 1 2 0 1 2 0
%e A204421 2 0 1 2 0 1
%e A204421 0 1 2 0 1 2
%e A204421 1 2 0 1 2 0
%e A204421 2 0 1 2 0 1
%e A204421 0 1 2 0 1 2
%t A204421 f[i_, j_] := Mod[i + j + 2, 3];
%t A204421 m[n_] := Table[f[i, j], {i, 1, n}, {j, 1, n}]
%t A204421 TableForm[m[8]] (* 8x8 principal submatrix *)
%t A204421 Flatten[Table[f[i, n + 1 - i],
%t A204421   {n, 1, 14}, {i, 1, n}]]    (* A204421 *)
%t A204421 Permanent[m_] :=
%t A204421   With[{a = Array[x, Length[m]]},
%t A204421    Coefficient[Times @@ (m.a), Times @@ a]];
%t A204421 Table[Permanent[m[n]], {n, 1, 22}]  (* A179079 *)
%Y A204421 Cf. A179079, A204263.
%K A204421 nonn,tabl
%O A204421 1,2
%A A204421 _Clark Kimberling_, Jan 15 2012