a(n) = 2*(10^n - 1)^2/27.A271528a(n) = 2*(10^n - 1)^2/27.Terms a(0) =0a(1) =6a(2) =726a(3) =73926a(4) =7405926a(5) =740725926a(6) =74073925926External referencesoeis: A271528