a(n) = n^(n-2)*(n+2)^(n-1).A006236a(n) = n^(n-2)*(n+2)^(n-1).Terms a(0) =1a(1) =4a(2) =75a(3) =3456a(4) =300125a(5) =42467328a(6) =8931928887External referencesoeis: A006236