Numbers k such that sigma(sigma(k^4)) == 0 (mod k^2).

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =16a(5) =19a(6) =38a(7) =76a(8) =152a(9) =304a(10) =608a(11) =1216a(12) =1824a(13) =3744a(14) =3840a(15) =4864a(16) =6400a(17) =7904a(18) =11520a(19) =14592a(20) =19200a(21) =21888a(22) =23712a(23) =24320a(24) =25536a(25) =32768a(26) =33696a(27) =34560a(28) =43776a(29) =71136