a(n) = n^8 - 1.

Terms

a(0) =0a(1) =255a(2) =6560a(3) =65535a(4) =390624a(5) =1679615a(6) =5764800a(7) =16777215a(8) =43046720a(9) =99999999a(10) =214358880a(11) =429981695a(12) =815730720a(13) =1475789055a(14) =2562890624a(15) =4294967295a(16) =6975757440a(17) =11019960575a(18) =16983563040a(19) =25599999999a(20) =37822859360a(21) =54875873535a(22) =78310985280a(23) =110075314175