Difference between the powers of two and the primes.

Terms

a(0) =0a(1) =1a(2) =3a(3) =9a(4) =21a(5) =51a(6) =111a(7) =237a(8) =489a(9) =995a(10) =2017a(11) =4059a(12) =8151a(13) =16341a(14) =32721a(15) =65483a(16) =131013a(17) =262083a(18) =524221a(19) =1048505a(20) =2097079a(21) =4194225a(22) =8388525a(23) =16777127a(24) =33554335a(25) =67108763a(26) =134217625a(27) =268435349a(28) =536870803a(29) =1073741711