a(n) = 54*2^n + 28 (n >= 1).

Terms

a(0) =136a(1) =244a(2) =460a(3) =892a(4) =1756a(5) =3484a(6) =6940a(7) =13852a(8) =27676a(9) =55324a(10) =110620a(11) =221212a(12) =442396a(13) =884764a(14) =1769500a(15) =3538972a(16) =7077916a(17) =14155804a(18) =28311580a(19) =56623132a(20) =113246236a(21) =226492444a(22) =452984860a(23) =905969692a(24) =1811939356a(25) =3623878684a(26) =7247757340a(27) =14495514652a(28) =28991029276a(29) =57982058524