For each of the following sequences (either arithmetic or geometric), find a possible function whose domain is the set of natural numbers and whose outputs are the terms of the sequence.
a. 2,5,8,11,14,dots
b. 2,4,8,16,32,dots
c. 2,2,2,2,dots
d. 2,2⁴/³,2⁵/³,2²,dots