User talk:Zxyzxy12321

$$ \begin{array}{rcl} a && = && a \\ b(k) && = && \left\{ \begin{array}{ll} 1      & (n=3n\ or\ 3n+1, n\in \mathbb{Z} ) \\ 2(n-1) & (n=3n+2) \end{array} \right.\\ n(k) && = && \left\{ \begin{array}{ll} 0 & (k = 0) \\ 1 & (k = 1) \\ b(k) \cdot n(k-1) + n(k-2) & otherwise \\ \end{array} \right.\\ d(k) && = && \left\{ \begin{array}{ll} 1 & (k = 0) \\ b(k) & (k = 1) \\ b(k) \cdot d(k-1) + d(k-2) & otherwise \end{array} \right.\\ \end{array} $$