Smallest x such that sigma(x) = n*phi(x), or -1 if no such x exists.

Terms

a(0) =1a(1) =3a(2) =2a(3) =14a(4) =56a(5) =6a(6) =12a(7) =42a(8) =30a(9) =168a(10) =2580a(11) =210a(12) =630a(13) =420a(14) =840a(15) =20790a(16) =416640a(17) =9240a(18) =291060a(19) =83160a(20) =120120a(21) =5165160a(22) =1719277560a(23) =43825320a(24) =26860680a(25) =277560360a(26) =1304863560a(27) =569729160a(28) =587133466920a(29) =16522145640