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

Terms

a(0) =1a(1) =1a(2) =5a(3) =25a(4) =193a(5) =1601a(6) =16741a(7) =190345a(8) =2509025a(9) =35825473a(10) =569012581a(11) =9716400761a(12) =180303804385