a(n) = 32*3^n + 18*2^n - 116 (n>=1).

Terms

a(0) =16a(1) =244a(2) =892a(3) =2764a(4) =8236a(5) =24364a(6) =72172a(7) =214444a(8) =638956a(9) =1907884a(10) =5705452a(11) =17079724a(12) =51165676a(13) =153349804a(14) =459754732a(15) =1378674604a(16) =4134844396a(17) =12402174124a(18) =37201804012a(19) =111595975084a(20) =334769051116