a(n) = lcm(d(n), sigma(n)).

Terms

a(0) =1a(1) =6a(2) =4a(3) =21a(4) =6a(5) =12a(6) =8a(7) =60a(8) =39a(9) =36a(10) =12a(11) =84a(12) =14a(13) =24a(14) =24a(15) =155a(16) =18a(17) =78a(18) =20a(19) =42a(20) =32a(21) =36a(22) =24a(23) =120a(24) =93a(25) =84a(26) =40a(27) =168a(28) =30a(29) =72