a(n) = (8*n+6)^4.

Terms

a(0) =1296a(1) =38416a(2) =234256a(3) =810000a(4) =2085136a(5) =4477456a(6) =8503056a(7) =14776336a(8) =24010000a(9) =37015056a(10) =54700816a(11) =78074896a(12) =108243216a(13) =146410000a(14) =193877776a(15) =252047376a(16) =322417936a(17) =406586896a(18) =506250000a(19) =623201296