Multiply by 1, add 1, multiply by 2, add 2, etc., start with 2.

Terms

a(0) =2a(1) =2a(2) =3a(3) =6a(4) =8a(5) =24a(6) =27a(7) =108a(8) =112a(9) =560a(10) =565a(11) =3390a(12) =3396a(13) =23772a(14) =23779a(15) =190232a(16) =190240a(17) =1712160a(18) =1712169a(19) =17121690a(20) =17121700a(21) =188338700a(22) =188338711a(23) =2260064532a(24) =2260064544a(25) =29380839072a(26) =29380839085a(27) =411331747190a(28) =411331747204