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

Terms

a(0) =1a(1) =1a(2) =6a(3) =42a(4) =392a(5) =4600a(6) =64752a(7) =1063216a(8) =19952256a(9) =421227648a(10) =9880951040a(11) =254960721664