3-wave sequence beginning with 2's.

Terms

a(0) =2a(1) =2a(2) =2a(3) =4a(4) =6a(5) =10a(6) =12a(7) =22a(8) =28a(9) =50a(10) =62a(11) =112a(12) =140a(13) =252a(14) =314a(15) =566a(16) =706a(17) =1272a(18) =1586a(19) =2858a(20) =3564a(21) =6422a(22) =8008a(23) =14430a(24) =17994a(25) =32424a(26) =40432a(27) =72856a(28) =90850a(29) =163706