a(n) = phi(prime(n)) - prime(phi(n)).

Terms

a(0) =-1a(1) =0a(2) =1a(3) =3a(4) =3a(5) =9a(6) =3a(7) =11a(8) =9a(9) =21a(10) =1a(11) =29a(12) =3a(13) =29a(14) =27a(15) =33a(16) =5a(17) =47a(18) =5a(19) =51a(20) =35a(21) =49a(22) =3a(23) =69a(24) =25a(25) =63a(26) =41a(27) =69a(28) =1a(29) =93