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

Terms

a(0) =0a(1) =1a(2) =0a(3) =6a(4) =36a(5) =380a(6) =4830a(7) =74382a(8) =1342712a(9) =27825912a(10) =651274650a(11) =16994464850a(12) =489240628932