a(n) = 3*a(n-1) + 7*a(n-2), with a(0) = 0, a(1) = 1.

Terms

a(0) =0a(1) =1a(2) =3a(3) =16a(4) =69a(5) =319a(6) =1440a(7) =6553a(8) =29739a(9) =135088a(10) =613437a(11) =2785927a(12) =12651840a(13) =57457009a(14) =260933907a(15) =1185000784a(16) =5381539701a(17) =24439624591a(18) =110989651680a(19) =504046327177