Expansion of g.f. (1+4*x)/((1-x)*(1+x)*(1-3*x)).

Terms

a(0) =1a(1) =7a(2) =22a(3) =70a(4) =211a(5) =637a(6) =1912a(7) =5740a(8) =17221a(9) =51667a(10) =155002a(11) =465010a(12) =1395031a(13) =4185097a(14) =12555292a(15) =37665880a(16) =112997641a(17) =338992927a(18) =1016978782a(19) =3050936350a(20) =9152809051a(21) =27458427157a(22) =82375281472a(23) =247125844420a(24) =741377533261