A hierarchical sequence (S(W2{3}c) - see A059126).

Terms

a(0) =11a(1) =54a(2) =161a(3) =396a(4) =887a(5) =1890a(6) =3917a(7) =7992a(8) =16163a(9) =32526a(10) =65273a(11) =130788a(12) =261839a(13) =523962a(14) =1048229a(15) =2096784a(16) =4193915a(17) =8388198a(18) =16776785a(19) =33553980a(20) =67108391a(21) =134217234a(22) =268434941a(23) =536870376a(24) =1073741267a(25) =2147483070a(26) =4294966697a(27) =8589933972a(28) =17179868543a(29) =34359737706