32605881domain: NAppears in sequencesa(n) = 7*(n+1)*binomial(n+5,7).at n=16A027812a(n) = (1/(1!*2!*3!*4!))*Sum_{1 <= x_1, x_2, x_3, x_4 <= n} |det V(x_1,x_2,x_3,x_4)|, where V(x_1,x_2,x_3,x_4) is the Vandermonde matrix of order 4.at n=19A133111