a(n) = 3*a(n-1) + 4*a(n-2) - a(n-3) + 3*a(n-4) + 4*a(n-5).

Terms

a(0) =1a(1) =4a(2) =13a(3) =51a(4) =204a(5) =819a(6) =3277a(7) =13108a(8) =52429a(9) =209715a(10) =838860a(11) =3355443a(12) =13421773a(13) =53687092a(14) =214748365a(15) =858993459a(16) =3435973836a(17) =13743895347a(18) =54975581389a(19) =219902325556a(20) =879609302221