a(n) = n! * Laguerre(n,-6).

Terms

a(0) =1a(1) =7a(2) =62a(3) =654a(4) =7944a(5) =108696a(6) =1649232a(7) =27422352a(8) =495057024a(9) =9631281024a(10) =200682406656