E.g.f.: -LambertW(-x/(1 + x)) / (1 + x).

Terms

a(0) =0a(1) =1a(2) =-2a(3) =9a(4) =-32a(5) =225a(6) =-1044a(7) =11515a(8) =-53696a(9) =1056321a(10) =-2809700a(11) =164953371a(12) =374457744a(13) =42734920657a(14) =415505963068