a(n) = C(n,8) + C(n,7) + C(n,6) + C(n,5) + C(n,4) + C(n,3) + C(n,2) + C(n,1).

Terms

a(0) =0a(1) =1a(2) =3a(3) =7a(4) =15a(5) =31a(6) =63a(7) =127a(8) =255a(9) =510a(10) =1012a(11) =1980a(12) =3796a(13) =7098a(14) =12910a(15) =22818a(16) =39202a(17) =65535a(18) =106761a(19) =169765a(20) =263949a(21) =401929a(22) =600369a(23) =880969a(24) =1271625a(25) =1807780a(26) =2533986a(27) =3505698a(28) =4791322a(29) =6474540