a(n) is the smallest positive integer that is coprime to n and has n divisors.

Terms

a(0) =1a(1) =3a(2) =4a(3) =15a(4) =16a(5) =175a(6) =64a(7) =105a(8) =100a(9) =567a(10) =1024a(11) =1925a(12) =4096a(13) =3645a(14) =784a(15) =945a(16) =65536a(17) =13475a(18) =262144a(19) =6237a(20) =1600a(21) =295245a(22) =4194304a(23) =25025a(24) =1296a(25) =2657205a(26) =4900a(27) =40095a(28) =268435456a(29) =3776773