To determine whether sequence k is geometric or arithmetic, we need more information or terms of the sequence. Without additional context, it is not possible to determine the nature of the sequence.
To write an equation to define sequence k recursively, we would need the initial term or terms of the sequence and the formula or rule that generates subsequent terms based on previous terms.
For term k(a), the values of a that make sense to use depend on the specific context of the sequence. Generally, any real number can be used as long as it fits the pattern or rule of the sequence. However, some values of a may not make sense if they result in non-numeric or nonsensical terms that do not align with the sequence's purpose or pattern. The suitability of values of a would need to be determined based on the specific sequence and its intended meaning or application.