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Properties of terms of OEIS A342810

General Mathematics 2021-06-11 v1

Abstract

The OEIS sequence A342810 contains the numbers that divide the smallest number that has the sum of their digits. It is proved that if a term xx has the form 3m×y3^m \times y where m2m \geq 2, then all prime factors of yy are prime divisors of solutions to 10n1  (modn)10^n \equiv 1 \; ( \bmod n). It is also proved that if a term xx has the form 3m×p×q3^m \times p \times q where m2m \geq 2, where pp is a prime divisor of a solution to 10n1  (modn)10^n \equiv 1 \; ( \bmod n) and where qq is the product of all other factors of the prime factorisation of xx, then all numbers 3m×pi×q3^m \times p^i \times q are also terms of the sequence A342810 for any integer ii.

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Cite

@article{arxiv.2106.05866,
  title  = {Properties of terms of OEIS A342810},
  author = {Rüdiger Jehn and Kester Habermann},
  journal= {arXiv preprint arXiv:2106.05866},
  year   = {2021}
}

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6 pages