a(1,n) as defined in A003148.

Terms

a(0) =1a(1) =-1a(2) =11a(3) =-39a(4) =633a(5) =-4065a(6) =86355a(7) =-818055a(8) =21370545a(9) =-270059265a(10) =8348125275a(11) =-132575387175