E.g.f.: Sum_{n>=0} x^n * cosh(n*x).

Terms

a(0) =1a(1) =1a(2) =2a(3) =9a(4) =72a(5) =665a(6) =6960a(7) =85057a(8) =1199744a(9) =19070865a(10) =336372480a(11) =6522635801a(12) =137996694528