a(n) = 2*a(n-1) + (n-1)*a(n-2).

Terms

a(0) =1a(1) =2a(2) =5a(3) =14a(4) =43a(5) =142a(6) =499a(7) =1850a(8) =7193a(9) =29186a(10) =123109a(11) =538078a(12) =2430355a(13) =11317646a(14) =54229907a(15) =266906858a(16) =1347262321a(17) =6965034370a(18) =36833528197a(19) =199037675054