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A surprising prime gap (Posted on 2016-07-27) Difficulty: 3 of 5
N is a positive integer. If you list the positive integers in rows of N such that the first row contains 1 to N, the second row contains N+1 to 2*N, and so on, then the first row with no prime is immediately followed by another row with no prime. What is N?

See The Solution Submitted by Math Man    
Rating: 5.0000 (1 votes)

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re: My solution | Comment 3 of 8 |
(In reply to My solution by Jer)

Any uniqueness, if it is unique, is due to the requirement that no other gap, of the single line length (in this case 16), existed before.


Double line gaps, without that requirement, do exist:

gap          ranges
17 15692 15708    15709 15725
18 16147 16164    16165 16182
21 19615 19635    19636 19656
22 25477 25498    25499 25520
25 31401 31425    31426 31450
27 31402 31428    31429 31455
31 31404 31434    31435 31465
39 155923 155961    155962 156000
41 155924 155964    155965 156005
42 360655 360696    360697 360738
47 370267 370313    370314 370360
48 370273 370320    370321 370368

  Posted by Charlie on 2016-07-30 09:13:56
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