Expansion of e.g.f. cosh( x^2/2 )/ (1-x).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =27a(5) =135a(6) =810a(7) =5670a(8) =45465a(9) =409185a(10) =4091850a(11) =45010350a(12) =540134595a(13) =7021749735a(14) =98304496290