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

Terms

a(0) =1a(1) =4a(2) =18a(3) =90a(4) =494a(5) =2946a(6) =18926a(7) =130066a(8) =950654a(9) =7353794a(10) =59954638a(11) =513333618a(12) =4601380766a(13) =43062556322a(14) =419742815726