a(n) = binomial(2*n+1, n-6).

Terms

a(0) =1a(1) =15a(2) =136a(3) =969a(4) =5985a(5) =33649a(6) =177100a(7) =888030a(8) =4292145a(9) =20160075a(10) =92561040a(11) =417225900a(12) =1852482996a(13) =8122425444a(14) =35240152720a(15) =151532656696a(16) =646626422970