Euler's rule states that the numbers and
are an amicable pair if
the three integers
|
(1)
| |||
|
(2)
| |||
|
(3)
|
are all prime numbers for some positive integers
and
satisfying
(Dickson 2005, p. 42). However, there are
many amicable pairs which do not satisfy Euler's
rule, so it is a sufficient but not necessary condition for amicability. Euler's rule is a generalization
of Thābit ibn Qurra rule.
The first few
for which Euler's rule is satisfied are
,
,
,
,
,
... (OEIS A094445 and A094446),
with no others for
, corresponding to the
triples
, (23, 47, 1151), (191, 383, 73727),
..., giving the amicable pairs (220, 284), (17296,
18416), (9363584, 9437056), ....