E.g.f.: 1/sqrt(1+x^2 - 2*x*cosh(x)).

Terms

a(0) =1a(1) =1a(2) =2a(3) =9a(4) =60a(5) =485a(6) =4680a(7) =53557a(8) =709968a(9) =10662633a(10) =178786080a(11) =3312164801a(12) =67201649856