Antiharmonic numbers: numbers k such that sigma_1(k) divides sigma_2(k).

Terms

a(0) =1a(1) =4a(2) =9a(3) =16a(4) =20a(5) =25a(6) =36a(7) =49a(8) =50a(9) =64a(10) =81a(11) =100a(12) =117a(13) =121a(14) =144a(15) =169a(16) =180a(17) =196a(18) =200a(19) =225a(20) =242a(21) =256a(22) =289a(23) =324a(24) =325a(25) =361a(26) =400a(27) =441a(28) =450a(29) =468