a(n) = Sum_{k=1..n} sigma_n(k).

Terms

a(0) =1a(1) =6a(2) =38a(3) =373a(4) =4461a(5) =68033a(6) =1202753a(7) =24757484a(8) =574608039a(9) =14925278329a(10) =427729375161