Expansion of (1+2*x) / (1-2*x-6*x^2).

Terms

a(0) =1a(1) =4a(2) =14a(3) =52a(4) =188a(5) =688a(6) =2504a(7) =9136a(8) =33296a(9) =121408a(10) =442592a(11) =1613632a(12) =5882816a(13) =21447424a(14) =78191744a(15) =285068032a(16) =1039286528a(17) =3788981248a(18) =13813681664a(19) =50361250816a(20) =183604591616a(21) =669376688128