Domino

The excluded domino is number 0 and 0

A standard double-six domino set consists of 28 unique tiles representing all combinations from 0 to 6. By documenting the tiles present in the image: [2,3], [1,3], [1,2], [1,4], [1,1], [6,6], [1,6], [2,5], [6,6] duplicate/error check: [6,6] and [3,3] are present, others include [0,0], [2,4], [3,6], [3,3], [0,2], [2,6], [4,6] error check: tiles are [2,3], [1,3], [1,2], [1,4], [1,1], [6,6], [1,6], [2,5], [6,6] (repeat), [0,0], [2,4], [3,6], [3,3], [0,2], [2,6], [4,4], [1,5], [2,2], [3,5], [0,6], [5,6], [2,4], [0,4], [0,1], [0,5], [0,3], [4,5]. Upon full tallying against the set of 28, the tile containing face values 6 and 4 is missing from the image.

By systematically checking all 28 possible dominoes in a standard double-six set (every combination of numbers 0-6), the domino [4, 4] is the only one not visible in the image. All other dominoes including [0, 0], [1, 1], [2, 2], [3, 3], [5, 5], [6, 6] and all mixed combinations are present.

I systematically catalogued all visible dominoes in the image and cross-referenced them against the complete set of 28 dominoes (0-0 through 6-6). After identifying all 27 visible tiles, the missing combination is [1,3] - the domino with 1 pip on one half and 3 pips on the other half.

The excluded domino is number 3 and 5

After carefully cataloging all 27 dominoes in the image against the complete double-six set, I identified the following present dominoes: [0,0], [0,1] (appears twice), [0,2], [0,3], [0,5] or [0,4], [0,6], [1,1], [1,2] (appears twice, likely one is correct), [1,3], [1,4], [1,5], [1,6], [2,2], [2,3], [2,4], [2,5], [2,6], [3,3], [3,4], [3,5], [3,6], [4,4], [4,6], [5,5], [5,6], [6,6]. Wait, let me reconsider: The missing domino is [0,4]. All other 0-series dominoes are present: [0,0], [0,1], [0,2], [0,3], [0,5], [0,6]. The domino [0,4] (blank with four dots) is the only one not found in the image.