Expansion of g.f.: (1+x^2)*(1+2*x^2)/(1-3*x+3*x^2-6*x^3+2*x^4-2*x^5).

Terms

a(0) =1a(1) =3a(2) =9a(3) =24a(4) =63a(5) =167a(6) =444a(7) =1179a(8) =3129a(9) =8306a(10) =22051a(11) =58539a(12) =155400a(13) =412535a(14) =1095149a(15) =2907266a(16) =7717839a(17) =20488343a(18) =54389880a(19) =144387411a(20) =383301505a(21) =1017540554a(22) =2701238539a(23) =7170907923a(24) =19036423288a(25) =50535499231a(26) =134155279397a(27) =356138541458a(28) =945431750839