The second left hand column of triangle A167591.

Terms

a(0) =-2a(1) =-8a(2) =-16a(3) =0a(4) =160a(5) =896a(6) =3584a(7) =12288a(8) =38400a(9) =112640a(10) =315392a(11) =851968a(12) =2236416a(13) =5734400a(14) =14417920a(15) =35651584a(16) =86900736a(17) =209190912a(18) =498073600a(19) =1174405120a(20) =2745171968a(21) =6366953472a(22) =14663286784a(23) =33554432000a(24) =76336332800a(25) =172738215936