Distance of 2^n from its nearest prime neighbor and in case of a tie, choose the smaller.

Terms

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