E.g.f exp(x)*cosh(x+x^2/2).

Terms

a(0) =1a(1) =1a(2) =2a(3) =7a(4) =23a(5) =71a(6) =242a(7) =925a(8) =3649a(9) =14593a(10) =61082a(11) =269039a(12) =1220375a(13) =5658823a(14) =27047386a(15) =133453429a(16) =674644673a(17) =3482517185a(18) =18399534386a(19) =99518837527a(20) =549283557463