display 8 bit ansi colors in terminal

script.sh

for i in {0..255} ; do
    printf "\x1b[38;5;%sm%5d\e[0m " "$i" "$i"
    if (( i == 15 )) || (( i > 15 )) && (( (i-15) % 6 == 0 )); then
        printf "\n";
    fi
done
for i in {0..255} ; do
    printf "\e[1m\x1b[38;5;%sm%10d\e[0m " "$i" "$i"
    if (( i == 15 )) || (( i > 15 )) && (( (i-15) % 6 == 0 )); then
        printf "\n";
    fi
done