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

Terms

a(0) =1a(1) =9a(2) =45a(3) =177a(4) =621a(5) =2049a(6) =6525a(7) =20337a(8) =62541a(9) =190689a(10) =578205a(11) =1746897a(12) =5265261a(13) =15844929a(14) =47633085a(15) =143095857a(16) =429680781a(17) =1289828769a(18) =3871059165a(19) =11616323217a(20) =34855261101a(21) =104578366209a(22) =313760264445a(23) =941331124977