A204440 Permanent of the n-th principal submatrix of A204439.

1, 1, 1, 2, 6, 20, 80, 384, 2016, 12096, 82080, 597888, 4783104, 41886720, 389145600, 3891456000, 41803776000, 472283136000, 5667397632000, 72153317376000, 959814696960000, 13437405757440000, 197840194965504000, 3028176742219776000, 48450827875516416000

Offset

0,4

Comments

Also the number of permutations pi in S_n such that pi(i) + i != 1 (mod 3) for all i. - Peter Kagey, Jan 25 2021

Links

Table of n, a(n) for n=0..24.

Mathematica

f[i_, j_] := Mod[(2 + i + j)^2, 3];
m[n_] := Table[f[i, j], {i, 1, n}, {j, 1, n}]
TableForm[m[8]] (* 8x8 principal submatrix *)
Flatten[Table[f[i, n + 1 - i],
  {n, 1, 14}, {i, 1, n}]]           (* A204439 *)
Join[{1}, Table[Permanent[m[n]], {n, 1, 22}]]  (* A204440 *)

Crossrefs

Cf. A204239, A204435.

Sequence in context: A108124 A186365 A245373 * A189839 A117574 A177481

Adjacent sequences: A204437 A204438 A204439 * A204441 A204442 A204443

Keyword

nonn

Author

Clark Kimberling, Jan 15 2012

Extensions

Typo in name corrected by Michel Marcus, Nov 11 2016

a(0) and a(23)-a(24) from Pontus von Brömssen, Jan 29 2021

Status

approved