echo randomly generated 5 letters from a-zA-Z for each number from 1 to 3000:
for i in $(seq $(shuf -i 1-3000 -n 1)); do echo $(shuf -i a-zA-Z -n 5); done
seq $(shuf -i 1-3000 -n 1) | tr "\n" "+" | sed 's/+$//' | xargs -l echo $(shuf -i a-zA-Z -n 5)