f(0)=n,f(1)=12n(n+1)f(0)=n,f(1)=\frac12n(n+1)f(0)=n,f(1)=21n(n+1) f(a)=1a+1(12(na+1+(n+1)a+1−1)−∑i≡n(mod2)a−2Ca+1if(i)){a∈N∣a>1}f(a)=\frac1{a+1}(\frac12(n^{a+1}+(n+1)^{a+1}-1)-\sum_{i\equiv n(mod2)}^{a-2}C^i_{a+1}f(i))\{a\in\mathbb{N}\mid a>1\} f(a)=a+11(21(na+1+(n+1)a+1−1)−∑i≡n(mod2)a−2Ca+1if(i)){a∈N∣a>1} 怎么求f(a)f(a)f(a)
