Numbers k such that sigma(k)*phi(k)*k is a square.

Terms

a(0) =1a(1) =6a(2) =40a(3) =84a(4) =162a(5) =672a(6) =2268a(7) =2480a(8) =3159a(9) =18144a(10) =58752a(11) =80262a(12) =91000a(13) =126360a(14) =140800a(15) =170688a(16) =358668a(17) =634725a(18) =718848a(19) =1063300a(20) =1089270a(21) =1255338a(22) =1701000a(23) =2319525a(24) =2869344a(25) =4189500a(26) =4608576a(27) =5642000a(28) =7834320a(29) =8506400