a(n) = a(n-3) - 5*a(n-2) + 5*a(n-1), a(0) = 1, a(1) = 3, a(2) = 10.

Terms

a(0) =1a(1) =3a(2) =10a(3) =36a(4) =133a(5) =495a(6) =1846a(7) =6888a(8) =25705a(9) =95931a(10) =358018a(11) =1336140a(12) =4986541a(13) =18610023a(14) =69453550a(15) =259204176a(16) =967363153a(17) =3610248435a(18) =13473630586a(19) =50284273908a(20) =187663465045a(21) =700369586271