数学符号k∈Z

国际统一符号,放心使用,没问题.
以下内容引自baidu屏蔽的w开头的某网站（你知道的）：
The integers (from the Latin integer, literally "untouched", hence "whole": the word entire comes from the same origin, but via French[1]) are formed by the natural numbers including 0 (0, 1, 2, 3, ...) together with the negatives of the non-zero natural numbers (−1, −2, −3, ...). Viewed as a subset of the real numbers, they are numbers that can be written without a fractional or decimal component, and fall within the set {... −2, −1, 0, 1, 2, ...}. For example, 65, 7, and −756 are integers; 1.6 and 1½ are not integers.
The set of all integers is often denoted by a boldface Z (or blackboard bold \mathbb{Z}, Unicode U+2124 ℤ), which stands for Zahlen (German for numbers, pronounced [ˈtsaːlən]).[2] The set \mathbb{Z}_n is the finite set of integers modulo n (for example, \mathbb{Z}_2=\{0,1\}).