Maximal sets of numbers not containing k + 1 pairwise coprime

Maximal sets of numbers not containing k + 1 pairwise coprime integers

For positive integers k; n let f(n; k) be the maximal cardinality of subsets of integers in the interval < 1; n > , which don't have k + 1 pairwise coprimes. The set E (n; k) of integers in < 1; n > , which are divisible by one of the rst k primes, certainly does not have k + 1 pairwise coprimes. Whereas we disproved in [1] an old conjecture of Erdos ([4], [5], [6], [7]) by showing that the eq...

On sequences containing at most 4 pairwise coprime integers

It has been conjectured by Erdó's that the largest number of natural numbers not exceeding n from which one cannot select k + l pairwise coprime integers, where k > 1 and n > p,, with p, denoting the zcth prime, is equal to the number of natural numbers not exceeding n which are multiples of at least one of the first k primes. It is known that the conjecture holds for k = 1 and 2. In this paper...

Maximal sets of numbers not containing k+1 pairwise coprimes and having divisors from a specified set of primes

Maximal sets of integers not containing k + 1 pairwise coprimes and having divisors from a specified set of primes

We find the formula for the cardinality of maximal set of integers from [1,. .. , n] which does not contain k + 1 pairwise coprimes and has divisors from a specified set of primes. This formula is defined by the set of multiples of the generating set, which does not depend on n. 1 Formulation of the result Let P = {p 1 < p 2 ,. . .} be the set of primes and N be the set of natural numbers. Writ...

Disjoint cliques and disjoint maximal independent sets of vertices in graphs

In this paper, we find lower bounds for the maximum and minimum numbers of cliques in maximal sets of pairwise disjoint cliques in a graph . By complementation, these yield lower bounds for the maximum and minimum numbers of independent sets in maximal sets of pairwise disjoint maximal independent sets of vertices in a graph . In the latter context, we show by examples that one of our bounds is...