Expansion of e.g.f.: exp(x^2/(1-x)).

Terms

a(0) =1a(1) =0a(2) =2a(3) =6a(4) =36a(5) =240a(6) =1920a(7) =17640a(8) =183120a(9) =2116800a(10) =26943840a(11) =374220000a(12) =5628934080a(13) =91122071040