45831035250domain: NAppears in sequencesExponential generating function: (1+3*x)/(1-2*x)^(7/2).at n=9A000457If n is even then a(n) = n!/( 2^(n/2)*(n/2)! ), otherwise a(n) = n!/( 3*2^((n-1)/2)*((n-3)/2)! ).at n=19A259877