- In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called elements, or terms). The number of elements (possibly infinite) is called the length of the sequence. Unlike a set, the same elements can appear multiple times at different positions in a sequence, and unlike a set, the order does matter. Formally, a sequence can be defined as a function from natural numbers (the positions of elements in the sequence) to the elements at each position. The notion of a sequence can be generalized to an indexed family, defined as a function from an arbitrary index set.
- Kahlotus Ridgetop Natural Area Preserve (dnr.wa.gov)
This 240-acre site preserves one of the last remaining examples of the vast native arid grassland that once covered much of the eastern Columbia Basin in Washington. A population of Piper’s daisy-a state-listed sensitive plant species that grows only in the Columbia Basin-occurs within the preserve. This site was designated a National Natural Landmark in 2011, in recognition of its nation-wide significance to natural area protection.