4-wave sequence beginning with 2s.

Terms

a(0) =2a(1) =2a(2) =2a(3) =2a(4) =4a(5) =6a(6) =8a(7) =14a(8) =18a(9) =20a(10) =38a(11) =52a(12) =60a(13) =112a(14) =150a(15) =170a(16) =320a(17) =432a(18) =492a(19) =924a(20) =1244a(21) =1414a(22) =2658a(23) =3582a(24) =4074a(25) =7656a(26) =10314a(27) =11728a(28) =22042a(29) =29698