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# Leyland number

A Leyland number is a number that can be expressed in the form $\displaystyle{ x^y+y^x }$, where x and y are positive integers greater 1 and x ≥ y. These numbers are named after Paul Leyland, who first studied these numbers in 1994. The first few nontrivial Leyland numbers are given by OEIS sequence A076980.

A Leyland prime is a Leyland number which is also a prime (see sequence A094133 in OEIS).

The second kind of numbers are of the form $\displaystyle{ x^y-y^x }$.

## Data

The data tables contains for every number the x and y values, the number of digits, the Leyland number[1], dates and persons of finding and proving if available and the program used to prove a prime.

### Leyland numbers

There are 1,814 numbers: 307 proven primes and 1,507 probable primes.

## Reservation history

### First kind (plus form)

Range x Range y Digits Reserved by Reserved Completed Found
3 - 1030 ~ 2 - 3000 Paul Leyland 1994 1997 88
1031 - 1050 ~ 700 - 2800 Paul Leyland 2001-06-04 2001-06-04 4
1051 - 1500 ~ 2000 - 4600 Andrey Kulsha 2001-06-03 2001-06-23 41
1501 - 1700 ~ 2600 - 5100 Paul Leyland 2001-06-05 2001-06-11 18
1701 - 2000 Christ van Willegen 2001-06-05 2001-06-09 23
2001 - 2200 Greg Childers 2001-06-07 2001-06-09 19
2201 - 2400 Greg Childers 2001-06-09 2001-06-12 17
2401 - 2600 Peter Liaskovsky 2001-08-31 2001-09-03 22
2601 - 2700 Paul Leyland 2001-07-24 2001-08-08 13
2701 - 2800 Greg Childers 2001-07-30 2001-07-31 7
2801 - 3000 Greg Childers 2001-07-31 2001-08-05 14
3001 - 3050 Sander Hoogendoorn 2001-06-14 2001-06-19 2
3051 - 3100 Peter Liaskovsky 2001-09-03 2001-09-05 6
3101 - 3200 Alexander Kuzmich 2001-09-16 2001-10-06 12
3201 - 3379 Leonid Muraviov 2001-11-28 2002-03-28 12
3380 - 3500 Andrey Kulsha 2002-04-19 2002-05-19 7
3501 - 4400 Paul Leyland 2001-12-21 2002-06-27 70
4401 - 4500 Greg Childers 2002-07-13 2002-08-13 9
4501 - 5000 Mark Rodenkirch 2002-09-07 2002-11-19 42
5001 - 5100 Paul Leyland 2003-06-13 2003-06-23 11
5101 - 5200 Paul Leyland 2003-06-23 2003-07-16 5
5201 - 5500 Greg Childers 2003-07-21 2003-09-17 17
5501 - 7500 Anatoly Selevich 2003-06-25 2004-08-07 154
20001 - 40000 11 - 200 Serge Batalov 2014-05-13 2014-05-14 17
15001 - 20000 1001 - 2000 Serge Batalov 2014-05-14 2014-05-14 20
40001 - 330000 11 - 17 Serge Batalov 2014-05-15 2014-05-16 3
330001 - 400000 11 - 17 Serge Batalov 2014-05-16 2014-05-17 -
400001 - 500000 11 - 17 Serge Batalov 2014-05-17 2014-05-19 -
20001 - 40000 201 - 400 Norbert Schneider 2014-07-09 2015-08-10
12051 - 12500 2001 - x-1 Norbert Schneider ? 2014-05-26 4
2501 - 3000 12501 - 15000 Vincent Gautier 2014-11-04 2014-11-14 6
300000 - 500000 18 Andrey Kulsha 2014-12-02
40001 - 50000 19 - 400 Norbert Schneider 2014-12-02 2015-10-23 -
50001 - 500000 19 - 25 Norbert Schneider 2015-01-26
12501 - 13000 3001 - x-1 Norbert Schneider 2015-10-23 2016-04-21 -
13000 - 15,000 Norbert Schneider 2019-03-27
20001 - 50000 401 - 800 Norbert Schneider 2016-04-21
20001 - 30000 801 - 1000 Dylan Delgado 2019-07-24

### Second kind (minus form)

Range x Range y Digits Reserved by Reserved Completed Found
3 - 10200 Norbert Schneider 2010 2015-04-03 1553
10201 - 10400 Norbert Schneider 2015-04-05 2015-06-15 30
10401 - 10600 Norbert Schneider 2015-07-23 2015-10-21 33
10601 - 10800 Norbert Schneider 2015-10-29 2016-01-21 20
10801 - 11000 Norbert Schneider 2016-01-27 2016-06-04 24
11000 - 11300 Norbert Schneider 2016-02-19 2016-10-19 34
11300 - 12400 Mark Rodenkirch 2016-03-26 2016-07-22 118
12401 - 12500 Norbert Schneider 2012-08-29 2013-08-27 13
12501 - 13000 Norbert Schneider 2016-04-10 35
13001 - 15000 41 - 1200 Norbert Schneider
15001 - 20000 41 - 100 Dylan Delgado 2019-08-04 2019-08-05 5
30001 - 30100 Norbert Schneider 2014-08-12 4
70001 - 100000 11 - 20 Dylan Delgado 2019-08-05 2019-08-17 1
70001 - 140000 Norbert Schneider

## Contribution of Leyland numbers

This graph can be found here: