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

Terms

a(0) =1a(1) =4a(2) =14a(3) =50a(4) =182a(5) =670a(6) =2482a(7) =9226a(8) =34358a(9) =128078a(10) =477698a(11) =1782202a(12) =6650086a(13) =24816094a(14) =92610194a(15) =345616490a(16) =1289839382a(17) =4813708270a(18) =17964928162a(19) =67045873306a(20) =250218302918a(21) =933826814078