a(n) = n*8^n.

Terms

a(0) =0a(1) =8a(2) =128a(3) =1536a(4) =16384a(5) =163840a(6) =1572864a(7) =14680064a(8) =134217728a(9) =1207959552a(10) =10737418240a(11) =94489280512a(12) =824633720832