a(n) is the least multiple of n, k*n say, such that phi(k) | sigma(k).

Terms

a(0) =1a(1) =2a(2) =3a(3) =12a(4) =15a(5) =6a(6) =14a(7) =56a(8) =270a(9) =30a(10) =264a(11) =12a(12) =78a(13) =14a(14) =15a(15) =4064a(16) =357a(17) =270a(18) =190a(19) =140a(20) =42a(21) =264a(22) =3956a(23) =168a(24) =27000a(25) =78a(26) =270a(27) =56a(28) =812a(29) =30