Difference between 2^n and the nearest prime less than or equal to 2^n.

Terms

a(0) =0a(1) =1a(2) =1a(3) =3a(4) =1a(5) =3a(6) =1a(7) =5a(8) =3a(9) =3a(10) =9a(11) =3a(12) =1a(13) =3a(14) =19a(15) =15a(16) =1a(17) =5a(18) =1a(19) =3a(20) =9a(21) =3a(22) =15a(23) =3a(24) =39a(25) =5a(26) =39a(27) =57a(28) =3a(29) =35