a(n) = n! * [x^n] exp(-n*x)/(1 - x)^n.

Terms

a(0) =1a(1) =0a(2) =2a(3) =6a(4) =72a(5) =620a(6) =8640a(7) =122346a(8) =2156672a(9) =41367672a(10) =905126400a(11) =21646532270a(12) =570077595648