Domino

The excluded domino is number 0 and 0

By systematically checking all 28 possible dominoes in a standard double-six set (all unique pairs from 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 pairs are present.

A standard double-six set has 28 tiles. The image shows 27 tiles. I counted and listed all the visible dominoes to find the missing one: [6, 5], [1, 2], [1, 5], [0, 1], [3, 5], [6, 6], [5, 5], [3, 2], [2, 6], [1, 1], [2, 3], [3, 3], [5, 2], [0, 0], [4, 5], [0, 5], [6, 4], [2, 2], [6, 3], [0, 4], [4, 6], [1, 4], [0, 2], [0, 3], [1, 6], [4, 3], [4, 2]. The numbers present are 0, 1, 2, 3, 4, 5, 6. All 7 doubles are present except for [4, 4]. The present doubles are: [0, 0], [1, 1], [2, 2], [3, 3], [5, 5], [6, 6]. Therefore, the [4, 4] domino is missing.

Counting pips on all visible tiles shows the digit 6 occurs two fewer times than it should in a complete double-six set (each number should appear 8 times). The only way to reduce the count of 6 by two is to remove the double-six tile, so the missing domino is [6,6].

After counting the occurrences of each number across all halves in the 27 dominoes, the number 6 appears only 6 times instead of 8, indicating the missing double-six domino.

The standard double-six domino set contains 28 dominoes, including the double-zero (0,0). The image shows 27 dominoes, and upon checking all possible pairs, the only missing domino is [0, 0] as all other pairs from (0,1) to (6,6) are present.

A standard double-six domino set contains 28 unique tiles, including seven doubles: [0,0], [1,1], [2,2], [3,3], [4,4], [5,5], and [6,6]. By examining the image, I can identify all doubles except [6,6]. The present doubles are: [0,0] (row 4, position 3), [1,1] (row 3, position 3 and row 6, position 1 - but upon closer inspection of the complete set logic), [2,2] (row 4, position 1), [3,3] (row 5, position 1), [4,4] (row 6, position 5), and [5,5] (row 1, position 1). The only double missing from the set is [6,6]. Additionally, checking the dominoes with 6-pips: [3,6] and [4,6] are present, but the double [6,6] is absent.