Twice A084773.

Terms

a(0) =2a(1) =12a(2) =104a(3) =1008a(4) =10272a(5) =107712a(6) =1150592a(7) =12451584a(8) =136053248a(9) =1497664512a(10) =16583583744a(11) =184511361024