a(n) = 11^n + 4^n - 1.

Terms

a(0) =1a(1) =14a(2) =136a(3) =1394a(4) =14896a(5) =162074a(6) =1775656a(7) =19503554a(8) =214424416a(9) =2358209834a(10) =25938473176a(11) =285315864914