macos terminal for loop

years=(2018 2019)
days=(74 274)

for year in "${years[@]}"; do
    for day in $(seq -w ${days[0]} ${days[1]}); do
               echo $year
               echo $day
    done
done

while [ <some test> ]
do
<commands>
done

for i in {1..100}; do echo http://www.example.com/${i}.jpg; done