Row 4 of table A111528.

Terms

a(0) =1a(1) =1a(2) =6a(3) =46a(4) =416a(5) =4256a(6) =48096a(7) =591536a(8) =7840576a(9) =111226816a(10) =1680157056a(11) =26918720896a(12) =455971214336