E.g.f.: exp( x*(1 + exp(3*x)) ).

Terms

a(0) =1a(1) =2a(2) =10a(3) =71a(4) =592a(5) =5777a(6) =64792a(7) =814025a(8) =11264176a(9) =169871633a(10) =2768582104a(11) =48412950929a(12) =902831609368