a(n) = A026301(n)/2^n.

Terms

a(0) =1a(1) =2a(2) =16a(3) =120a(4) =882a(5) =6468a(6) =47680a(7) =354224a(8) =2652688a(9) =20008864a(10) =151853312a(11) =1158365824a(12) =8873772392a(13) =68219456080a(14) =526025997824