Abstract:A k-strong Giuga number is a composite integer such that n−1 j=1 j n−1 ≡ −1 (mod n). We consider the congruence n−1 j=1 j k(n−1) ≡ −1 (mod n) for each k ∈ N (thus extending Giuga's ideas for k = 1). In particular, it is proved that a pair (n, k) with composite n satisfies this congruence if and only if n is a Giuga number and λ(n) | k(n − 1). In passing, we establish some new characterizations of Giuga numbers and study some properties of the numbers n satisfying λ(n) | k(n − 1). k-Сильне число Гюга-це складен… Show more
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