Expansion of (1-x)/(1 - 4*x + x^2 + x^3).

Terms

a(0) =1a(1) =3a(2) =11a(3) =40a(4) =146a(5) =533a(6) =1946a(7) =7105a(8) =25941a(9) =94713a(10) =345806a(11) =1262570a(12) =4609761a(13) =16830668a(14) =61450341a(15) =224360935a(16) =819162731a(17) =2990839648a(18) =10919834926a(19) =39869337325a(20) =145566674726a(21) =531477526653