(dseq nper end)(dseq nper start end)(dseq nper start end step)
Distributed sequence for a range of numbers.  The overall sequence is derived
from `start`, `end`, and `step` as per core `range` and with the same defaults.
Each map task will receive `nper` values, the final task receiving fewer if the
length of the number of values is not evenly divisible by `nper`.