a(n) = practical(2^n) where practical(n) is the n-th practical number (A005153).

Terms

a(0) =1a(1) =2a(2) =6a(3) =18a(4) =42a(5) =108a(6) =270a(7) =594a(8) =1350a(9) =3008a(10) =6678a(11) =14620a(12) =31724a(13) =67712a(14) =143792a(15) =305856a(16) =651126a(17) =1377918a(18) =2908308a(19) =6120672a(20) =12848472a(21) =26854938a(22) =55963260a(23) =116389896a(24) =241526012a(25) =500796416a(26) =1037764968a(27) =2147851712a(28) =4440630150a(29) =9176799780