Least k such that phi(k*n-1) = phi(k*n+1), or -1 if no such k exists.

Terms

a(0) =5a(1) =4a(2) =3a(3) =2a(4) =1a(5) =106a(6) =21a(7) =1a(8) =1a(9) =39282a(10) =1a(11) =53a(12) =135a(13) =65014a(14) =5a(15) =9489a(16) =171a(17) =361a(18) =27a(19) =19641a(20) =7a(21) =13133a(22) =141a(23) =6326a(24) =3a(25) =6978a(26) =1a(27) =32507a(28) =375a(29) =13094