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Template:Sequence of the Day for February 14

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Intended for: February 14, 2012

Timetable

  • First draft entered by Alonso del Arte on November 6, 2011
  • Draft reviewed by Daniel Forgues on February 14, 2016
  • Draft to be approved by January 14, 2012

Yesterday's SOTD * Tomorrow's SOTD

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A063990: Amicable numbers.

{ 220, 284, 1184, 1210, 2620, 2924, 5020, ... }
Notice how for example
σ (220)  −  220 = 284
and
σ (284)  −  284 = 220
. Amicable numbers are numbers belonging to amicable pairs.
Note that numbers belonging to an amicable pair are not always adjacent in the above sequence: see A259180 for amicable pairs
(x, y), x < y,
such that
y
follows
x
, ordered by increasing
x
.