Numbers having exactly four anti-divisors.

Terms

a(0) =13a(1) =18a(2) =40a(3) =41a(4) =61a(5) =84a(6) =100a(7) =169a(8) =289a(9) =421a(10) =784a(11) =1024a(12) =1104a(13) =1296a(14) =3121a(15) =5776a(16) =9216a(17) =12544a(18) =12769a(19) =13924a(20) =16129a(21) =17956a(22) =24649a(23) =32761a(24) =33024a(25) =35344a(26) =36721a(27) =36864a(28) =38809a(29) =71821