Math problem

[LGM]

Here is another solution. The patern appears to be 2^x-1. I would suspect that the next solution is at 63, but 31 took long enough to prove and my algorythm uses prime numbers with the mod function to find matches, so I don't want to look up another 32 prime numbers to make it that far.

N=31
15,23,24
15,22,25
15,21,26
15,20,27
15,19,28
15,18,29
15,17,30
15,16,31
14,23,25
14,22,24
14,21,27
14,20,26
14,19,29
14,18,28
14,17,31
14,16,30
13,23,26
13,22,27
13,21,24
13,20,25
13,19,30
13,18,31
13,17,28
13,16,29
12,23,27
12,22,26
12,21,25
12,20,24
12,19,31
12,18,30
12,17,29
12,16,28
11,23,28
11,22,29
11,21,30
11,20,31
11,19,24
11,18,25
11,17,26
11,16,27
10,23,29
10,22,28
10,21,31
10,20,30
10,19,25
10,18,24
10,17,27
10,16,26
9,23,30
9,22,31
9,21,28
9,20,29
9,19,26
9,18,27
9,17,24
9,16,25
8,23,31
8,22,30
8,21,29
8,20,28
8,19,27
8,18,26
8,17,25
8,16,24
7,27,28
7,26,29
7,25,30
7,24,31
7,19,20
7,18,21
7,17,22
7,16,23
7,11,12
7,10,13
7,9,14
7,8,15
6,27,29
6,26,28
6,25,31
6,24,30
6,19,21
6,18,20
6,17,23
6,16,22
6,11,13
6,10,12
6,9,15
6,8,14
5,27,30
5,26,31
5,25,28
5,24,29
5,19,22
5,18,23
5,17,20
5,16,21
5,11,14
5,10,15
5,9,12
5,8,13
4,27,31
4,26,30
4,25,29
4,24,28
4,19,23
4,18,22
4,17,21
4,16,20
4,11,15
4,10,14
4,9,13
4,8,12
3,29,30
3,28,31
3,25,26
3,24,27
3,21,22
3,20,23
3,17,18
3,16,19
3,13,14
3,12,15
3,9,10
3,8,11
3,5,6
3,4,7
2,29,31
2,28,30
2,25,27
2,24,26
2,21,23
2,20,22
2,17,19
2,16,18
2,13,15
2,12,14
2,9,11
2,8,10
2,5,7
2,4,6
1,30,31
1,28,29
1,26,27
1,24,25
1,22,23
1,20,21
1,18,19
1,16,17
1,14,15
1,12,13
1,10,11
1,8,9
1,6,7
1,4,5
1,2,3