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I generated this sequence 2102012210101111222011212000200220212200120102112020222211102212100010011012, find next 4 digits and explain the reason.
Note that this is a ternary sequence. All digits are generated by few rules, no digit is random or arbitrary.

Hint:

The sequence generated is periodic and the period is equal to 80 digits, but 80 (as any number greater than 3) does not appear in the rules

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2 Answers 2

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After starting 2, 1, 0, 2,

each subsequent digit is obtained by summing modulo 3 the third- and fourth-to-last digits. Therefore, the next 4 digits are 1 + 0 = 1, 0 + 1 = 1, 1 + 2 = 0, 2 + 1 = 0.

This corresponds to a

ternary linear-feedback shift register based on the primitive polynomial x4 + x3 + 2 over the finite field GF(3), so it generates a ternary m-sequence. This means that the sequence of 4-digit strings produced (2102, 1020, 0201, 2012, ...) cycles through all 34 - 1 = 80 possibilities besides 0000 before repeating periodically.

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  • $\begingroup$ Good explanation about how the sequence has been generated! $\endgroup$ Commented Apr 11 at 15:41
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The next four digits are

1100

Because

The first fourty digits are the same as the next thirty-six digits but with the 1s and 2s switched. So I'm assuming the next four continue that pattern.

Beyond that, I'm haven't figured out how the sequence was generated.

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  • $\begingroup$ +1 for the correct digits, now I'm waiting for an answer explaining how the sequence was generated $\endgroup$ Commented Apr 10 at 16:02
  • $\begingroup$ @Livio I think you might want to check out noedne's answer then, I believe that might give the correct explanation. $\endgroup$ Commented Apr 11 at 10:07

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