Numbers n such that sigma(n) and sigma(sigma(n)) are both perfect squares.

Terms

a(0) =1a(1) =343a(2) =10680a(3) =11448a(4) =11832a(5) =12760a(6) =12920a(7) =13470a(8) =14360a(9) =14526a(10) =15064a(11) =15198a(12) =15486a(13) =15752a(14) =16194a(15) =16264a(16) =16376a(17) =16390a(18) =16472a(19) =16910a(20) =17110a(21) =18734a(22) =20366a(23) =20654a(24) =20822a(25) =21094a(26) =21122a(27) =21158a(28) =21598a(29) =21843