Expansion of (1+x-2*x^2)/(1-21*x^2-7*x^3).

Terms

a(0) =1a(1) =1a(2) =19a(3) =28a(4) =406a(5) =721a(6) =8722a(7) =17983a(8) =188209a(9) =438697a(10) =4078270a(11) =10530100a(12) =88714549a(13) =249679990a(14) =1936716229a(15) =5864281633a(16) =42418800739a(17) =136706927896a(18) =931844786950