E.g.f.: 1 + Sum_{n>=1} 2*cosh(n*x) * x^(n^2).

Terms

a(0) =1a(1) =2a(2) =0a(3) =6a(4) =48a(5) =10a(6) =2880a(7) =14a(8) =53760a(9) =725778a(10) =645120a(11) =359251222a(12) =6082560a(13) =42032390426a(14) =49201152