a(n) = A000085(n) - A000079(n-1).

Terms

a(0) =0a(1) =0a(2) =0a(3) =2a(4) =10a(5) =44a(6) =168a(7) =636a(8) =2364a(9) =8984a(10) =34672a(11) =138104a(12) =564408a(13) =2382288a(14) =10333152a(15) =46173968a(16) =211733776a(17) =997182752a(18) =4809439296a(19) =23758139808a(20) =119951644320a(21) =618882541760