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Template:Sequence of the Day for July 23

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Intended for: July 23, 2012

Timetable

  • First draft entered by Alonso del Arte on July 22, 2011
  • Draft reviewed by Daniel Forgues on July 23, 2011
  • Draft to be approved by June 23, 2012
Yesterday's SOTD * Tomorrow's SOTD

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A000945: The Euclid–Mullin sequence:
a (1) = 2
; for
n   ≥   2
,
a (n)
is the smallest prime factor of
1 +
n  − 1

k  = 1
a (k)
.
{ 2, 3, 7, 43, 13, 53, 5, 6221671, ... }

The first four terms coincide with the Sylvester sequence (where each term is the product of all preceding terms plus 1) (A000058), a [thus strictly increasing] infinite coprime sequence whose terms may be prime or composite.