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The nth term is 4n - 3
The special divisibility rule of 17 is "Take the difference of the rest of the digits and the last digit times 5." For instance: 17 1 - 7 * 5 = 1 - 35 = -34 which is divisible by 17.
There are 10 possible combinations so 60 possible permutations. The combinations are:(1, 3, 21), (1, 5, 19), (1, 7, 17), (1, 9, 15), (1, 11, 13),(3, 5, 17), (3, 7, 15), (3, 9, 13), (5, 7, 13), (5, 9, 11).
1 5 9 13 17 21
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