Permanent of the n-th principal submatrix of A204435.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =6a(5) =16a(6) =80a(7) =384a(8) =1728a(9) =12096a(10) =82080a(11) =525312a(12) =4783104a(13) =41886720a(14) =349056000a(15) =3891456000a(16) =41803776000a(17) =429981696000