E.g.f.: -exp(2*x)*LambertW(-x).

Terms

a(0) =0a(1) =1a(2) =6a(3) =33a(4) =216a(5) =1865a(6) =21228a(7) =303765a(8) =5222864a(9) =104540337a(10) =2383558740a(11) =60933722069