Talking in a competition scenario, it is your fight and you have to win so you will want the best method, and for that few users even copy paste the array itself for some problems you can see here also.
With respect to good programming practice, it is always better to know the idea and then pre-compute or use the values in the way you want. And, just copy pasting an array is not a good programming practice, generally. As @kuruma said, in questions involving prime numbers, catalan numbers, it is better to pre-compute, but again if the given domain in the problem is small enough many users tend to copy paste an array.
For example, this problem CLMBSTRS of Feb Challenge had good test cases so copy pasting dint work, but pre-computing did. My Solution with copy pasted array as comment.
This with pre-computing.