Q(2,n), where Q(m,k) is defined in A127080 and A127137.

Terms

a(0) =1a(1) =1a(2) =0a(3) =-3a(4) =-4a(5) =15a(6) =48a(7) =-105a(8) =-624a(9) =945a(10) =9600a(11) =-10395a(12) =-175680a(13) =135135a(14) =3790080a(15) =-2027025a(16) =-95235840a(17) =34459425a(18) =2752081920a(19) =-654729075a(20) =-90328089600a(21) =13749310575a(23) =-316234143225