Expansion of e.g.f.: sqrt( -LambertW(x)*LambertW(-x)/x^2 ).

Terms

a(0) =1a(1) =0a(2) =2a(3) =0a(4) =76a(5) =0a(6) =9816a(7) =0a(8) =2731408a(9) =0a(10) =1327394080a(11) =0a(12) =998915378880a(13) =0a(15) =0a(17) =0a(19) =0a(21) =0a(23) =0a(25) =0