Least k >= 0 such that phi(n) * sigma(n) + k^2 is a perfect square, or -1 if impossible.

Terms

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