a(n) = (n^3 - n^2)*4^n.

Terms

a(0) =0a(1) =64a(2) =1152a(3) =12288a(4) =102400a(5) =737280a(6) =4816896a(7) =29360128a(8) =169869312a(9) =943718400a(10) =5075107840a(11) =26575110144a(12) =136096776192a(13) =683973541888