a(n) = lcm_{d|n} sigma(d).

Terms

a(0) =1a(1) =3a(2) =4a(3) =21a(4) =6a(5) =12a(6) =8a(7) =105a(8) =52a(9) =18a(10) =12a(11) =84a(12) =14a(13) =24a(14) =24a(15) =3255a(16) =18a(17) =156a(18) =20a(19) =126a(20) =32a(21) =36a(22) =24a(23) =420a(24) =186a(25) =42a(26) =520a(27) =168a(28) =30a(29) =72