a(n) = Sum_{k=0..n} floor(C(n,k)/2).

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =7a(5) =14a(6) =30a(7) =60a(8) =127a(9) =254a(10) =510a(11) =1020a(12) =2046a(13) =4092a(14) =8188a(15) =16376a(16) =32767a(17) =65534a(18) =131070a(19) =262140a(20) =524286a(21) =1048572a(22) =2097148a(23) =4194296a(24) =8388606a(25) =16777212a(26) =33554428a(27) =67108856a(28) =134217724a(29) =268435448