#!/bin/sh
blk=( 7 15 {34..51} {70..87} {106..123} {142..159} {178..195} {214..231} {244..255} )
rem=8
add=1
for i in {0..255}; do
	printf "\x1b[48;5;${i}m"
	printf "\x1b[38;5;15m"
	if [ $i -eq $blk ]; then
		printf "\x1b[38;5;0m"
		blk=(${blk[@]:1})
	fi
	printf "%8s" "${i}"
	printf "\x1b[0m"
	[ $(( ( $i + $add ) % $rem )) -eq 0 ] && echo
	[ $i -eq 15 ] && rem=6 && add=3
done
unset blk rem add