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# User:Marina Ibrishimova

I came across the following sequences while working on a problem for over the last ten years of my life.

1. The sequence generated by powers of 2 mod n when n is the product of 2 distinct safe primes. The sequence was published in the OEIS.org with sequence number A269453 [1]. Here are the first few terms of the sequence:

12, 20, 30, 44, 33, 92, 110, 116, 69, 174, 164, 230, 212, 246, 290, 318, 332, 356, 410, 253, 452, 249, 530, 534, 524, 638, 678, 692, 716, 830, 393, 902, 764, 890, 932, 956, 1038, 1166, 1130, 537, 1004, 573, 1334, 1124, 1310, 1172, 1398, 717, 753, 1436, 1730, 913, 1886, 1686, 1790

2. The sequence is the sequence of the products of two distinct safe primes, which is now published in the OEIS.org under sequence number A269452 [2])

24, 40, 60, 88, 132, 184, 220, 232, 276, 348, 328, 460, 424, 492, 580, 636, 664, 712, 820, 1012, 904, 996, 1060, 1068, 1048, 1276, 1356, 1384, 1432, 1660, 1572, 1804, 1528, 1780, 1864, 1912, 2076, 2332, 2260, 2148, 2008, 2292, 2668, 2248, 2620, 2344, 2796, 2868, 3012, 2872, 3460, 3652, 3772, 3372

3. Looking at these 2 sequences made me discover a third sequence, which consists of safe primes not congruent to -1 mod 8 and it is now published with a sequence number A269454 [3].

5, 11, 59, 83, 107, 179, 227, 347, 467, 563, 587, 1019, 1187, 1283, 1307, 1523, 1619, 1907, 2027, 2099, 2459, 2579, 2819, 2963, 3203, 3467, 3779, 3803, 3947, 4139, 4259, 4283, 4547, 4787, 5099, 5387, 5483, 5507, 5939, 6659, 6779, 6827, 6899, 7187, 7523

The next couple of sequences I came up with involve the Collatz conjecture, which is an open problem in Mathematics. 2 of these sequence were published.

4. The first sequence of the Collatz trio is the sequence of Collatz primes A276260 ([4]), and it only has 9 terms. If a 10th term exists, it would have to be really, really large.

5, 13, 17, 53, 61, 107, 251, 283, 1367

5. The second sequence is the sequence of Collatz products, and it has many more terms. It is published under the sequence number A276290 [5] .

25, 35, 55, 65, 77, 85, 95, 115, 133, 143, 145, 155, 161, 185, 203, 205, 209, 215, 217, 235, 253, 259, 265, 287, 295, 305, 329, 341, 355, 365, 371, 391, 395, 403, 407, 415, 427, 437, 445

I keep a math blog where I talk about my favorite Math problems and it can be found at [6]