a(n) = 4*a(n-1) + 9*a(n-2).

Terms

a(0) =0a(1) =1a(2) =4a(3) =25a(4) =136a(5) =769a(6) =4300a(7) =24121a(8) =135184a(9) =757825a(10) =4247956a(11) =23812249a(12) =133480600a(13) =748232641a(14) =4194255964a(15) =23511117625a(16) =131792774176a(17) =738771155329