C((n+1)*2^(n-1),n)/(n+1).A136464C((n+1)*2^(n-1),n)/(n+1).Terms a(0) =1a(1) =1a(2) =5a(3) =140a(4) =18278a(5) =10187344a(6) =23427955408External referencesoeis: A136464