E.g.f.: -log(1+log(1+log(1-x))).

Terms

a(0) =1a(1) =3a(2) =15a(3) =105a(4) =947a(5) =10472a(6) =137337a(7) =2085605a(8) =36017472a(9) =697407850a(10) =14969626900a(11) =352877606716