@johnalx ,
Welcome to the forum.
Re: the “data statement,” note the use of DATA also imparts the SAVE attribute to the variable, essentially making it a static variable and adversely impacting thread-safety. Coders may not want that attribute in modern applications.
An option to consider if implied-do is of interest is
a = [( xx, integer :: i = 1, n )] !<-- xx can be a constant such as zero, or a valid expression involving `i`