a(n) = 2^(floor(n/2))+2^(floor(n/2)-1)-2^(floor((n-1)/3)).

Terms

a(0) =2a(1) =2a(2) =4a(3) =4a(4) =10a(5) =8a(6) =20a(7) =20a(8) =40a(9) =40a(10) =88a(11) =80a(12) =176a(13) =176a(14) =352a(15) =352a(16) =736a(17) =704a(18) =1472a(19) =1472a(20) =2944a(21) =2944a(22) =6016a(23) =5888a(24) =12032a(25) =12032a(26) =24064a(27) =24064a(28) =48640a(29) =48128