错排
> dn=(n−1)×(dn−1+dn−2)d_n=(n-1)×(d_{n-1}+d_{n-2}) dn =(n−1)×(dn−1 +dn−2 )
>
> D1=0,D2=1D_1=0, D_2=1D1 =0,D2 =1
卡特兰
> hn=(4n−2)×hn−1n+1h_n=\frac{(4n-2)×h_{n-1}}{n+1} hn =n+1(4n−2)×hn−1
>
> H1=1,H2=2H_1=1, H_2=2H1 =1,H2 =2
斯特林第二类
> snm=m×sn−1m+sn−1m−1s^m_n=m×s^{m}_{n-1}+s^{m-1}_{n-1} snm =m×sn−1m +sn−1m−1
>
> S00=1,S01=0,S10=0S^0_0=1, S^1_0=0, S^0_1=0S00 =1,S01 =0,S10 =0