Let $\\{a_m\\}_{m}\subset \mathbb R$ be a sequence such that $\sum_ma_m$ is absolutely convergence to $a$ and consider $\\{(a_m,a_m,...,a_m)\\}_m\subset \mathbb R^n$ which is convergence by $d_1$ to $na$
Let $\\{a_m\\}_{m}\subset \mathbb R$ be a sequence such that $\sum_ma_m$ is absolutely convergence to $a$ and consider $\\{(a_m,a_m,...,a_m)\\}_m\subset \mathbb R^n$ which is convergence by $d_1$ to $na$