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Template:Sequence of the Day for November 12

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Intended for: November 12, 2012

Timetable

  • First draft entered by Alonso del Arte on April 1, 2012
  • Draft reviewed by Daniel Forgues on April 3, 2012
  • Draft to be approved by October 12, 2012
Yesterday's SOTD * Tomorrow's SOTD

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A158624: Upper limit of backward value (base 10) of
5n, n ∈ ℕ ∪ 0
.
0.52656795787...
The “backward value (base 10)” of 25 is 0.52; of 125, 0.521; of 625, 0.526; of 3125, 0.5213; etc. Since
5n   ≡   5  (mod 10), n   ≥   1,
it follows that the backward value of
5n, n   ≥   1,
starts out 0.5. Furthermore, since
5n   ≡   25  (mod 100), n   ≥   2,
the next to least significant digit is 2 for all
n   ≥   2
, and the backward value therefore in those cases always starts out 0.52. It is a little harder to prove that any subsequent digit of this constant is either 5, 6, 7, 8 or 9 but not 0, 1, 2, 3 or 4.

See also: A158625 Lower limit of backward value (base 10) of
5n
.