login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A267076 Amicable numbers with property that both members of the amicable pair have the same sopfr (as defined in A001414). 2
98671027044178875, 110707233329488965, 116112602631024285, 138000805229957475, 347701424633005443, 373158429641554557, 581028000695478105, 650656605928265895, 1057340336068271871, 1192941584025936129, 1317952177931347245, 1597858331524012755 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Both members of the amicable pair with same sopfr are listed in the sequence but are not necessarily adjacent.

The terms shown have 17, 18 digits (7 terms) and 19 digits (four terms).

Comment from N. J. A. Sloane, Jun 07 2016: (Start)

Sergei Chernykh has conducted several searches for amicable pairs in the 18-digit range (here p and q are the largest prime factors):

1) All pairs of the form (m*p^k1, n*q^k2) where k1 > 1 _OR_ k2 > 1

2) All pairs of the form (m*p, n*q) where m < 2*10^11 _AND_ n < 2*10^11

3) Current exhaustive search has already found all pairs of the form (m*p^k1, n*q^k2) where p < 21818622 for any k1, q, k2

If we combine the results of these searches it is easy to see that the remaining undiscovered pairs can only have the form (m*p, n*q) where their largest prime factors are p > 21818622 and q < 10000000 (2*10^18 / 2*10^11), so they can't have the same sopfr.

This means that all 18-digit members of A267076 are already known. There are no new ones. (End)

Sergei Chernykh with BOINC completed the amicable pairs list with 20 digits.

In their ongoing search for 21-digit amicable numbers  Sergei Chernykh and BOINC have so far found the following numbers: 130292188156891334007, 137813613144174393993, 208010335478545813941, 220018224493331050059, 250217395764910459875, 271313659794405815325, 276109509594435349833, 349735430520058090167, 370496519153268119073, 402333253352868456927, 781727874026691579075, 886084603302962180925. - Sven Simon Feb 26 2021

LINKS

Sven Simon, Table of n, a(n) for n = 1..22

Sergei Chernykh, Amicable pairs list

EXAMPLE

To illustrate that 347701424633005443 and 373158429641554557 belong to the sequence:

347701424633005443 = 3*7^3*11*13*19*37*41*59*131*10607, sopfr(n) = 10942.

373158429641554557 = 3*7^2*11*13*19*311*383*839*9349, sopfr(n) = 10942.

CROSSREFS

Cf. A001414, A063990, A091340, A259180.

Sequence in context: A257168 A104837 A008923 * A146088 A217592 A092697

Adjacent sequences:  A267073 A267074 A267075 * A267077 A267078 A267079

KEYWORD

nonn

AUTHOR

Sven Simon, Jan 10 2016

EXTENSIONS

Entry revised by Michel Marcus and N. J. A. Sloane, Jan 23 2016

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 21 08:06 EDT 2021. Contains 348150 sequences. (Running on oeis4.)