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

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =2a(5) =3a(6) =6a(7) =11a(8) =19a(9) =35a(10) =64a(11) =117a(12) =215a(13) =399a(14) =744a(15) =1394a(16) =2621a(17) =4946a(18) =9362a(19) =17772a(20) =33825a(21) =64527a(22) =123361a(23) =236298a(24) =453438a(25) =871543a(26) =1677721a(27) =3234162a(28) =6242685a(29) =12064514