Expansion of e.g.f. exp(2*(exp(x) - 1)).

Terms

a(0) =1a(1) =2a(2) =6a(3) =22a(4) =94a(5) =454a(6) =2430a(7) =14214a(8) =89918a(9) =610182a(10) =4412798a(11) =33827974a(12) =273646526a(13) =2326980998a(14) =20732504062a(15) =192982729350