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

Terms

a(0) =1a(1) =0a(2) =2a(3) =-6a(4) =12a(5) =0a(6) =-240a(7) =2520a(8) =-18480a(9) =60480a(10) =937440a(11) =-21621600a(12) =220207680a(13) =-311351040a(14) =-34490776320a(15) =724669545600