T(0) = 1, T(1) = 1, T(n) = (n - 1) T(n - 1) + (n - 1) T(n - 2) + 2n^2 - 5n + 4 + (n - 1)(subfactorial(n - 1) n + subfactorial(n - 2) (n - 1))

• Lenguaje natural
• Entrada matemática