Ideal quasi-Cauchy sequences

*Correspondence: [email protected]; [email protected] 1Department of Mathematics, Maltepe University, Marmara Eğİtİm Köyü, TR 34857, Maltepe, İstanbul, Turkey Full list of author information is available at the end of the article Abstract An ideal I is a family of subsets of positive integersN which is closed under taking finite unions and subsets of its elements. A sequence (xn) of real numbers is said to be I-convergent to a real number L if for each ε > 0, the set {n : |xn – L| ≥ ε} belongs to I. We introduce I-ward compactness of a subset of R, the set of real numbers, and I-ward continuity of a real function in the senses that a subset E of R is I-ward compact if any sequence (xn) of points in E has an I-quasi-Cauchy subsequence, and a real function is I-ward continuous if it preserves I-quasi-Cauchy sequences where a sequence (xn) is called to be I-quasi-Cauchy when ( xn) is I-convergent to 0. We obtain results related to I-ward continuity, I-ward compactness, ward continuity, ward compactness, ordinary compactness, ordinary continuity, δ-ward continuity, and slowly oscillating continuity. MSC: Primary 40A35; secondary 40A05; 40G15; 26A15