Dominoes are small rectangular tiles with dots called spots or pips embossed at both halves of the tiles. a standard "double-six" domino set has 28 tiles: one for each of the unordered pair of integers from (0,0) to (6,6). in general, a "double-n" domino set would consist of domino tiles for each unordered pair of integers from (0,0) to (n,n). determine all values of n for which one constructs a ring made up of all the tiles in a double-n domino set.
