How many sextuples of positive integers are there for which conditions and are satisfied?
Solution
To each chosen from the set of integers , there is a pair of integers satisfying the conditions and . Therefore, there are exactly such pairs . Finding sextuples satisfying the conditions of this problem is equivalent to finding triplets of pairs from this set of pairs. In fact, if we order the pairs chosen as starting with the smallest and increasing the value of (hence ), then associate this triplet with the sextuple . We then see that it satisfies the condition of the problem. Conversely, any such sextuple arises from a triplet of pairs from the set of pairs considered above. Therefore, the number we seek is given by .
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