a(n) = 8*a(n-1) - 8*a(n-2), a(0)=1, a(1)=4.

Terms

a(0) =1a(1) =4a(2) =24a(3) =160a(4) =1088a(5) =7424a(6) =50688a(7) =346112a(8) =2363392a(9) =16138240a(10) =110198784a(11) =752484352a(12) =5138284544a(13) =35086401536a(14) =239584935936