This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A204436 #20 Jan 31 2021 10:24:24
%S A204436 1,1,1,2,6,16,80,384,1728,12096,82080,525312,4783104,41886720,
%T A204436 349056000,3891456000,41803776000,429981696000,5667397632000,
%U A204436 72153317376000,883878137856000,13437405757440000,197840194965504000,2813727217287168000,48450827875516416000
%N A204436 Permanent of the n-th principal submatrix of A204435.
%C A204436 Also the number of permutations pi in S_n such that pi(i) + i != 0 (mod 3) for all i. - _Peter Kagey_, Jan 25 2021
%t A204436 f[i_, j_] := Mod[(i + j)^2, 3];
%t A204436 m[n_] := Table[f[i, j], {i, 1, n}, {j, 1, n}]
%t A204436 TableForm[m[8]] (* 8x8 principal submatrix *)
%t A204436 Flatten[Table[f[i, n + 1 - i],
%t A204436 {n, 1, 14}, {i, 1, n}]] (* A204435 *)
%t A204436 Join[{1},Table[Permanent[m[n]], {n, 1, 22}]] (* A204436 *)
%Y A204436 Cf. A204235.
%K A204436 nonn
%O A204436 0,4
%A A204436 _Clark Kimberling_, Jan 15 2012
%E A204436 a(0) and a(23)-a(24) from _Pontus von Brömssen_, Jan 29 2021