a(1)=1; thereafter a(n) = 2^(number of bits in binary expansion of a(n-1)) + 1 + a(n-1).

Terms

a(0) =1a(1) =4a(2) =13a(3) =30a(4) =63a(5) =128a(6) =385a(7) =898a(8) =1923a(9) =3972a(10) =8069a(11) =16262a(12) =32647a(13) =65416a(14) =130953a(15) =262026a(16) =524171a(17) =1048460a(18) =2097037a(19) =4194190a(20) =8388495a(21) =16777104a(22) =33554321a(23) =67108754a(24) =134217619a(25) =268435348a(26) =536870805a(27) =1073741718a(28) =2147483543a(29) =4294967192