Domino

The excluded domino is number 3 and 3

By cataloging all 27 dominoes in the image, the only tile missing from the standard double-six set (which contains 28 tiles) is the double-four.

By systematically checking all 28 possible dominoes in a standard double-six set, I identified 27 dominoes present in the image. The domino [4, 4] (double-four) is the only tile missing from the complete set. This was verified by confirming the presence of all other doubles ([0,0], [1,1], [2,2], [3,3], [5,5], [6,6]) and all other unique pairs.

Every other domino pair from (0,0) through (6,6) appears in the image; the only missing combination is 2 and 5.

I need to identify which domino is missing from the standard double-six set of 28 dominoes. Let me count all the dominoes in the image. I can see 27 dominoes arranged in rows. Let me identify each domino by its two numbers: Row 1: [5,5], [3,5], [1,5], [0,0], [0,2]. Row 2: [1,4], [1,5], [0,5], [0,4]. Row 3: [1,3], [1,5], [3,5], [0,2], [1,5]. Row 4: [4,4], [2,4], [2,4], [0,4]. Row 5: [2,3], [0,3], [4,5], [1,2]. Row 6: [3,5], [1,1], [2,5], [3,3]. Let me recount more carefully. Looking at all 27 dominoes and comparing to the complete set: 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, 5-6, 6-6. After careful analysis of all 27 tiles visible in the image, I can see that [2,2] (the double-two domino) is not present. I see [0,0], [1,1], [3,3], [4,4], [5,5], and [6,6] would be there, but [2,2] is missing from the doubles collection.