Domino

A standard double-six set contains 28 tiles. By cataloging the tiles in the image, all tiles except the double-six [6,6] are present. Specifically, the following are found: [0,0], [0,1], [0,2], [0,3], [0,4], [0,5], [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], and [5,6].

After carefully counting and identifying all 27 dominoes in the provided ASCII art representation, all combinations from the standard double-six set are present except for the [3|5] domino.

A careful scan of the 27 shown tiles reveals every combination of pips from 0–6 except the tile with six pips on both ends; no domino in the image shows 6|6, so the missing domino is [6,6]

A standard double-six set has 28 unique dominoes. Counting the presence of each pair, all pairs except [3, 4] are accounted for in the image. The missing domino is therefore [3, 4].

By analyzing the dot counts and identifying all 27 present dominoes, I determined that the domino [1,1] is the only one from the standard double-six set that does not appear in the image. The dominoes containing 1 that are present are: [0,1], [1,2], [1,3], [1,4], [1,5], and [1,6]. The double [1,1] is missing, and counting the occurrences of the number 1 confirms this (6 appearances instead of the expected 8 in a full set, or 7 if a non-double containing 1 were missing).