Template:Sequence of the Day for February 14

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

.