how to write a loop that estimates in bash code example

Example 1: loop bash

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

Example 2: bash loop

#!/bin/bash

# A simple bash "for loop" example below...
# This loop will run 5 times, and will echo the number in sequence as it goes.
# Mind the double . between the {}
# Note how the variable is called with the $ prefix, which can be done within the "" quotes!

for i in {1..5}
do
   echo "This is loop number $i"
done

# To achieve the same in a single line is also simple

for i in {1..5};do echo "this is loop number $i";done

## Happy coding, my homies! <3

Example 3: bash for loop

for VARIABLE in file1 file2 file3
do
	command1 on $VARIABLE
	command2
	commandN
done