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

Terms

a(0) =0a(1) =1a(2) =8a(3) =54a(4) =320a(5) =1750a(6) =9072a(7) =45276a(8) =219648a(9) =1042470a(10) =4862000a(11) =22355476a(12) =101582208a(13) =457002364a(14) =2038517600a(15) =9026235000a(16) =39710085120a(17) =173712232710a(18) =756088415280