a(n) = 2^(n-3)*binomial(n,4).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =2a(5) =20a(6) =120a(7) =560a(8) =2240a(9) =8064a(10) =26880a(11) =84480a(12) =253440a(13) =732160a(14) =2050048a(15) =5591040a(16) =14909440a(17) =38993920a(18) =100270080a(19) =254017536a(20) =635043840a(21) =1568931840a(22) =3835166720a(23) =9285140480a(24) =22284337152a(25) =53057945600a(26) =125409689600a(27) =294440140800a(28) =687026995200