Egyptian Fractions with Restrictions

Abstract

Let $T_o(k)$ denote the number of solutions of $\sum_{i=1}^k\frac 1{x_i}=1$ in odd numbers $1 1$ in $S(p_1, p_2,..., p_t)$ is more than 1. In this paper we study $T_o(k)$ and $T_k(p_1,..., p_t)$. Three of our results are: 1) $T_o(2k+1)\ge (\sqrt 2)^{(k+1)(k-4)}$ for all $k\ge 4$; 2) if the inverse sum of all elements $s_j>1$ in $S(p_1, p_2,..., p_t)$ is more than 1, then $T_k(p_1,..., p_t)\not= 0$ for infinitely many $k$ and the set of these $k$ is the union of finitely many arithmetic progressions; 3) there exists two constants $k_0=k_0(p_1,..., p_t)>1$ and $c=c(p_1,..., p_t)>1$ such that for any $k>k_0$ we have either $T_k(p_1,..., p_t)= 0$ or $T_k(p_1,..., p_t)>c^k$.