A000168(n+1) - A000139(n).

Terms

a(0) =0a(1) =8a(2) =52a(3) =372a(4) =2894a(5) =23966a(6) =208086a(7) =1874508a(8) =17390158a(9) =165248499a(10) =1601857338a(11) =15790898316a(12) =157915304928