a(n) = 344*7^n/21 - 128/3 (n>=1).

Terms

a(0) =72a(1) =760a(2) =5576a(3) =39288a(4) =275272a(5) =1927160a(6) =13490376a(7) =94432888a(8) =661030472a(9) =4627213560a(10) =32390495176a(11) =226733466488