Number of reversible strings with n beads of 4 colors. If more than 1 bead, not palindromic.

A032087

Number of reversible strings with n beads of 4 colors. If more than 1 bead, not palindromic.

Terms

    a(0) =4a(1) =6a(2) =24a(3) =120a(4) =480a(5) =2016a(6) =8064a(7) =32640a(8) =130560a(9) =523776a(10) =2095104a(11) =8386560a(12) =33546240a(13) =134209536a(14) =536838144a(15) =2147450880a(16) =8589803520a(17) =34359607296a(18) =137438429184a(19) =549755289600

External references