Expansion of e.g.f. (1+3x-3x^2)/(1-x)^2.

Terms

a(0) =1a(1) =5a(2) =12a(3) =42a(4) =192a(5) =1080a(6) =7200a(7) =55440a(8) =483840a(9) =4717440a(10) =50803200a(11) =598752000a(12) =7664025600a(13) =105859353600