a(n) = 4^n * A000108(n+1).

Terms

a(0) =1a(1) =8a(2) =80a(3) =896a(4) =10752a(5) =135168a(6) =1757184a(7) =23429120a(8) =318636032a(9) =4402970624a(10) =61641588736a(11) =872465563648