http://mt-creations.fr/repeater.php An insight about representing sub-sequence of numbers or range.
http://adsecurite.fr/?seledka=site-de-rencontre-bingo&f4f=e5 http://www.cs.utexas.edu/~EWD/ewd08xx/EWD831.PDF
Subsequence_of_numbers (PDF, local copy)