Column 1 of table in A067640.

Terms

a(0) =2a(1) =20a(2) =174a(3) =1504a(4) =13300a(5) =120744a(6) =1122198a(7) =10638464a(8) =102541428a(9) =1002305040a(10) =9914663308a(11) =99085515840a(12) =999104604784