Domino

The excluded domino is number 0 and 0

After counting all combinations in the standard 28-tile double-six set, the [0, 5] domino is missing from the image. All other combinations (0-0, 0-1, 0-2, 0-3, 0-4, 0-6, 1-1, 1-2, 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, 4-5, 4-6, 5-5, 5-6, and 6-6) are present.

By systematically cataloging all visible dominoes in the image and comparing them to the complete set of 28 double-six dominoes (which includes all combinations of numbers 0-6), the domino [2, 4] is the only one that does not appear among the 27 dominoes shown. All other 27 unique domino combinations are present.

After systematically cataloging all 27 visible dominoes in the image and comparing them to a complete standard double-six set of 28 tiles, the double-blank (0-0) domino is missing. All other combinations from 0-0 through 6-6 are accounted for except for the tile with zero pips on both halves.

In a complete double-six set each digit 0–6 appears 7 times across the tiles. I counted the occurrences of each face in the image; 0–5 each appear 7 times but the 6-face appears only 5 times, so the missing tile must be the double six [6,6] (which would supply the two missing 6-faces).

After examining the 27 dominoes in the image and comparing against the complete set of 28, the [5-3] domino is absent. All other combinations from [0-0] to [6-6] are present.

After analyzing all visible dominoes in the image, I identified 27 dominoes from the standard double-six set. By checking for the presence of each double (0-0, 1-1, 2-2, 3-3, 4-4, 5-5, 6-6) and all other combinations, I found that [3,3] (three dots on both sides) is the only domino not present in the image. The doubles [0,0], [1,1], [2,2], [4,4], [5,5] are all visible, and while [6,6] could potentially be mistaken for [5,5], the [3,3] double is distinctly absent with its characteristic three-dot diagonal pattern on both sides.