E.g.f.: exp(exp(x) - 1)*(exp(3*x) - 2*exp(x) + 1).

Terms

a(0) =0a(1) =1a(2) =9a(3) =52a(4) =283a(5) =1561a(6) =8930a(7) =53411a(8) =334785a(9) =2199034a(10) =15119621a(11) =108644581a(12) =814474176a(13) =6358910949a(14) =51615342685a(15) =434865155292