A204436 Permanent of the n-th principal submatrix of A204435.

1, 1, 1, 2, 6, 16, 80, 384, 1728, 12096, 82080, 525312, 4783104, 41886720, 349056000, 3891456000, 41803776000, 429981696000, 5667397632000, 72153317376000, 883878137856000, 13437405757440000, 197840194965504000, 2813727217287168000, 48450827875516416000

Offset

0,4

Comments

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

Links

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

Mathematica

f[i_, j_] := Mod[(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}]]       (* A204435 *)
Join[{1}, Table[Permanent[m[n]], {n, 1, 22}]]   (* A204436 *)

Crossrefs

Cf. A204235.

Sequence in context: A345246 A137858 A074740 * A135068 A147950 A147941

Adjacent sequences: A204433 A204434 A204435 * A204437 A204438 A204439

Keyword

nonn

Author

Clark Kimberling, Jan 15 2012

Extensions

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

Status

approved