a(n) = a(n-1) - (n-1)*a(n-2), with a(0) = 1, a(1) = 2.

Terms

a(0) =1a(1) =2a(2) =1a(3) =-3a(4) =-6a(5) =6a(6) =36a(7) =0a(8) =-252a(9) =-252a(10) =2016a(11) =4536a(12) =-17640a(13) =-72072a(14) =157248a(15) =1166256a(16) =-1192464a(17) =-19852560a(18) =419328a(19) =357765408a(20) =349798176a(21) =-6805509984a(22) =-14151271680a(23) =135569947968a(24) =461049196608