split data numbers into two columns in shell script

I have numbers from 1 to 1000 in file ($y).

for i in {1..1000}
do
echo "$i" >> $y
done

I want to split numbers into two column in the file(user enters the filename that indicates "$y").

1    501
.    .
.    .
500  1000 

like this.

I tried ‘split -l500 $y’ and ‘column -t ‘ command but couldnt get result.

>Solution :

What I would do:

printf '%d\t%d\n' {1..100} 
1    2
3    4
5    6
[...]

Then:

printf '%d\t%d\n' {1..100} | while read i; do
        echo "$i" >> "$y"
    done