Numbers k such that phi(sigma(k))/sigma(phi(k)) = 2.

Terms

a(0) =2a(1) =4a(2) =16a(3) =18a(4) =64a(5) =100a(6) =450a(7) =1458a(8) =4096a(9) =4624a(10) =28900a(11) =36450a(12) =62500a(13) =65536a(14) =130050a(15) =262144a(16) =281250a(17) =1062882a(18) =1336336a(19) =3334800a(20) =7064400a(21) =8352100a(22) =10156800a(23) =10534050a(24) =18062500a(25) =21193200a(26) =22781250a(27) =26572050a(28) =37584450a(29) =39062500