E.g.f.: exp(2 * (exp(x) - 1 - x - x^2 / 2 - x^3 / 6)).

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =2a(5) =2a(6) =2a(7) =2a(8) =142a(9) =506a(10) =1346a(11) =3170a(12) =53198a(13) =375234a(14) =1880738a(15) =7919082a(16) =72104190a(17) =678488362a(18) =5164781154a(19) =33220643026a(20) =271431061614