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

Terms

a(0) =0a(1) =2a(2) =5a(3) =24a(4) =169a(5) =1572a(6) =18208a(7) =252676a(8) =4088138a(9) =75571648a(10) =1571427096a(11) =36304942704a(12) =922615912656