a(n) = n*d(n), where d(n) = number of divisors of n (A000005).

Terms

a(0) =1a(1) =4a(2) =6a(3) =12a(4) =10a(5) =24a(6) =14a(7) =32a(8) =27a(9) =40a(10) =22a(11) =72a(12) =26a(13) =56a(14) =60a(15) =80a(16) =34a(17) =108a(18) =38a(19) =120a(20) =84a(21) =88a(22) =46a(23) =192a(24) =75a(25) =104a(26) =108a(27) =168a(28) =58a(29) =240