a(n) = (2^n + 1)^3.

Terms

a(0) =8a(1) =27a(2) =125a(3) =729a(4) =4913a(5) =35937a(6) =274625a(7) =2146689a(8) =16974593a(9) =135005697a(10) =1076890625a(11) =8602523649a(12) =68769820673a(13) =549957165057