a(n) = 9*binomial(2n,n-4)/(n+5).

Terms

a(0) =1a(1) =9a(2) =54a(3) =273a(4) =1260a(5) =5508a(6) =23256a(7) =95931a(8) =389367a(9) =1562275a(10) =6216210a(11) =24582285a(12) =96768360a(13) =379629720a(14) =1485507600a(15) =5801732460a(16) =22626756594a(17) =88152205554a(18) =343176898988