Exponential generating function (1-x^2)^(-1/x).

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =13a(5) =71a(6) =391a(7) =2836a(8) =21729a(9) =198829a(10) =1939501a(11) =21515836a(12) =254169301a(13) =3319328299a(14) =45979476635a(15) =691443303916