G.f.: (1+3*x+2*x^2)/((1-x)*(1-2*x^2)).

Terms

a(0) =1a(1) =4a(2) =8a(3) =14a(4) =22a(5) =34a(6) =50a(7) =74a(8) =106a(9) =154a(10) =218a(11) =314a(12) =442a(13) =634a(14) =890a(15) =1274a(16) =1786a(17) =2554a(18) =3578a(19) =5114a(20) =7162a(21) =10234a(22) =14330a(23) =20474a(24) =28666a(25) =40954a(26) =57338a(27) =81914a(28) =114682a(29) =163834