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