Expansion of e.g.f.: (1-x)/(2-exp(x)).

Terms

a(0) =1a(1) =0a(2) =1a(3) =4a(4) =23a(5) =166a(6) =1437a(7) =14512a(8) =167491a(9) =2174746a(10) =31374953a(11) =497909380a(12) =8619976719a(13) =161667969646