Expansion of (1-x+x^2)/((1+x^2)(1-4x+x^2)).

Terms

a(0) =1a(1) =3a(2) =11a(3) =42a(4) =157a(5) =585a(6) =2183a(7) =8148a(8) =30409a(9) =113487a(10) =423539a(11) =1580670a(12) =5899141a(13) =22015893a(14) =82164431a(15) =306641832a(16) =1144402897a(17) =4270969755a(18) =15939476123a(19) =59486934738a(20) =222008262829a(21) =828546116577