Permanent of the n-th principal submatrix of A204547.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =4a(5) =8a(6) =72a(7) =288a(8) =864a(9) =3456a(10) =35424a(11) =212544a(12) =1088640a(13) =6220800a(14) =75064320a(15) =600514560a(16) =4147200000a(17) =31684608000a(18) =440681472000