E.g.f.: exp(x + x^4/4).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =7a(5) =31a(6) =91a(7) =211a(8) =1681a(9) =12097a(10) =57961a(11) =209881a(12) =1874071a(13) =17842111a(14) =117303187a(15) =575683291a(16) =5691897121a(17) =65641390081a(18) =544238393041