Expansion of e.g.f. (1-x^4)/(1-x-x^4).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =240a(6) =2160a(7) =20160a(8) =201600a(9) =2540160a(10) =36288000a(11) =558835200a(12) =9101030400a(13) =161902540800