E.g.f.: (exp(exp(x)-1)-1)^2.

Terms

a(0) =0a(1) =0a(2) =2a(3) =12a(4) =64a(5) =350a(6) =2024a(7) =12460a(8) =81638a(9) =567888a(10) =4180848a(11) =32470834a(12) =265219332a(13) =2271692124a(14) =20350705418a(15) =190216812260