a(n) = 2^(n-1) * prime(n).

Terms

a(0) =2a(1) =6a(2) =20a(3) =56a(4) =176a(5) =416a(6) =1088a(7) =2432a(8) =5888a(9) =14848a(10) =31744a(11) =75776a(12) =167936a(13) =352256a(14) =770048a(15) =1736704a(16) =3866624a(17) =7995392a(18) =17563648a(19) =37224448a(20) =76546048a(21) =165675008a(22) =348127232a(23) =746586112a(24) =1627389952a(25) =3388997632a(26) =6912212992a(27) =14361296896