Number of values generated by the algorithm given as first comment.

Terms

a(0) =2a(1) =4a(2) =8a(3) =8a(4) =12a(5) =34a(6) =58a(7) =96a(8) =188a(9) =334a(10) =574a(11) =1046a(12) =1874a(13) =3308a(14) =5928a(15) =10608a(16) =18872a(17) =33694a(18) =60194a(19) =107338a(20) =191542a(21) =341950a(22) =610146a(23) =1088790a(24) =1943262a(25) =3467858a(26) =6188534a(27) =11044356a(28) =19709736a(29) =35173564