arXiv subjects
Publications and source records attributed to Kancou D. Fall.
We study the concatenation of two $k$-generalized Pell numbers. More precisely, we determine all solutions of the equation $P_n^{(k)} = P_m^{(k)} \cdot 10^{d} + P_p^{(k)}$, where $d$ is the number of decimal digits of $P_p^{(k)}$. We prove that for $k \ge 3$ there are no solutions, while for $k = 2$ the only solution is $P_4 = 12 = 1\|2$.
We study multiplicative dependence between terms of the $k$-generalized Pell sequence $(P_n^{(k)})_{n\ge 2-k}$, defined by the linear recurrence \[ P_n^{(k)} = 2P_{n-1}^{(k)} + P_{n-2}^{(k)} + \dots + P_{n-k}^{(k)}, \] with initial conditions $P_0^{(k)} = \dots = P_{-(k-2)}^{(k)} = 0$ and $P_1^{(k)} = 1$. For $k\ge 2$ we determine all pairs $(m,n)$ with $n>m\ge 0$ such that $P_n^{(k)}$ and $P_m^{(k)}$ are multiplicatively dependent. The main result states that the only solutions occur for very small $k,m,n$ (which are listed explicitly). The proof uses lower bounds for linear forms in logarithms (Matveev), the Baker-Davenport reduction algorithm, and a computational search.