E.g.f.: exp(x + 2*x^2 + 3*x^3 + 4*x^4).

Terms

a(0) =1a(1) =1a(2) =5a(3) =31a(4) =241a(5) =1661a(6) =16861a(7) =181315a(8) =2091041a(9) =25320601a(10) =354057301a(11) =5149373351a(12) =78917379025