a(n) = 2*A001610(n).

Terms

a(0) =0a(1) =4a(2) =6a(3) =12a(4) =20a(5) =34a(6) =56a(7) =92a(8) =150a(9) =244a(10) =396a(11) =642a(12) =1040a(13) =1684a(14) =2726a(15) =4412a(16) =7140a(17) =11554a(18) =18696a(19) =30252a(20) =48950a(21) =79204a(22) =128156a(23) =207362a(24) =335520a(25) =542884a(26) =878406a(27) =1421292a(28) =2299700a(29) =3720994