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

Terms

a(0) =0a(1) =1a(2) =10a(3) =63a(4) =336a(5) =1650a(6) =7722a(7) =35035a(8) =155584a(9) =680238a(10) =2939300a(11) =12584726a(12) =53488800a(13) =225990180a(14) =950094810a(15) =3977737875a(16) =16594533120a(17) =69018792150a(18) =286296636780