E.g.f.: exp(x/(1 + x + x^2 + x^3)).

Terms

a(0) =1a(1) =1a(2) =-1a(3) =-5a(4) =1a(5) =161a(6) =31a(7) =-8021a(8) =-14335a(9) =686881a(10) =2925631a(11) =-91860229a(12) =-583959551a(13) =15741408385a(14) =169511794271