In the expansion of $${(1 - 3x + 3{x^2} - {x^3})^{2n}}$$, the middle term is

Using mathematical induction, the numbers $${a_n}$$'s are defined by $${a_0} = 1,{a_{n + 1}} = 3{n^2} + n + {a_n},(n \ge 0)$$. Then, $${a_n}$$ is equal to

If $$49^n+16n+P$$ is divisible by 64 for all $$n\in N$$, then the least negative integral value of P is

$${2^{3n}} - 7n - 1$$ is divisible by