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

Terms

a(0) =1a(1) =2a(2) =8a(3) =36a(4) =216a(5) =1440a(6) =11520a(7) =100800a(8) =1008000a(9) =10886400a(10) =130636800a(11) =1676505600a(12) =23471078400a(13) =348713164800