Some Congruences Involving Binomial Coefficient and Fermat Quotient
Wei-Wei Qi
TL;DR
The paper addresses high-order congruences for sums involving d^{-k} binomial(x, k) binomial(x+k, k) divided by binomial(2k, k) with p-adic x and Fermat quotients. It introduces a key summation identity and uses binomial algebra, harmonic-number relations, and Wolstenholme-type results to obtain p-adic congruences modulo p^4 (and p^5 in special cases), culminating in Theorems 1.1, 1.3, and 1.5. Corollaries are derived by specializing x to particular values such as -1/2, -1/3, -1/4, and -1/6, and by applying auxiliary harmonic-number congruences. Overall, the work extends the landscape of binomial-coefficient congruences in the p-adic setting and provides explicit, higher-order congruence formulas useful for number theory and combinatorics.
Abstract
In this paper, we investigate some congruences involving sums of $\frac{d^{-k}{x\choose k}{x+k\choose k}}{2k \choose k}$, where $x$ be a $p$-adic integer, $k$ be a non-negative integer, and $d$ $(d\neq 0)$ be a rational number.
