a(n) = 5*a(n-1) + 4*a(n-2) with a(0)=1, a(1)=4.

Terms

a(0) =1a(1) =4a(2) =24a(3) =136a(4) =776a(5) =4424a(6) =25224a(7) =143816a(8) =819976a(9) =4675144a(10) =26655624a(11) =151978696a(12) =866515976a(13) =4940494664a(14) =28168537224a(15) =160604664776a(16) =915697472776