To install click the Add extension button. That's it.

The source code for the WIKI 2 extension is being checked by specialists of the Mozilla Foundation, Google, and Apple. You could also do it yourself at any point in time.

4,5
Kelly Slayton
Congratulations on this excellent venture… what a great idea!
Alexander Grigorievskiy
I use WIKI 2 every day and almost forgot how the original Wikipedia looks like.
Live Statistics
English Articles
Improved in 24 Hours
Added in 24 Hours
What we do. Every page goes through several hundred of perfecting techniques; in live mode. Quite the same Wikipedia. Just better.
.
Leo
Newton
Brights
Milds

From Wikipedia, the free encyclopedia

Thabit prime
Named afterThābit ibn Qurra
No. of known terms62
Conjectured no. of termsInfinite
Subsequence ofThabit numbers
First terms2, 5, 11, 23, 47, 191, 383, 6143, 786431
Largest known term3×211,895,718 − 1
OEIS indexA007505

In number theory, a Thabit number, Thâbit ibn Kurrah number, or 321 number is an integer of the form for a non-negative integer n.

The first few Thabit numbers are:

2, 5, 11, 23, 47, 95, 191, 383, 767, 1535, 3071, 6143, 12287, 24575, 49151, 98303, 196607, 393215, 786431, 1572863, ... (sequence A055010 in the OEIS)

The 9th Century mathematician, physician, astronomer and translator Thābit ibn Qurra is credited as the first to study these numbers and their relation to amicable numbers.[1]

YouTube Encyclopedic

  • 1/5
    Views:
    517
    670
    228 338
    11 886
    24 880
  • ✪ Interesting Thabit Ibn Qurra Facts
  • ✪ Thābit ibn Qurra
  • ✪ As Subhu Bada Min~ Zain Bhikha
  • ✪ One of the Best Naat in the World in Arabic - Qaseeda Hassan Bin Sabit قصيدة حسان بن ثابت
  • ✪ Lives of Sahaba 11 - Sunni beliefs about The Sahaba (The Companions) - Sh. Dr. Yasir Qadhi

Transcription

Contents

Properties

The binary representation of the Thabit number 3·2n−1 is n+2 digits long, consisting of "10" followed by n 1s.

The first few Thabit numbers that are prime (Thabit primes or 321 primes):

2, 5, 11, 23, 47, 191, 383, 6143, 786431, 51539607551, 824633720831, ... (sequence A007505 in the OEIS)

As of October 2015, there are 62 known prime Thabit numbers. Their n values are :[2][3][4]

0, 1, 2, 3, 4, 6, 7, 11, 18, 34, 38, 43, 55, 64, 76, 94, 103, 143, 206, 216, 306, 324, 391, 458, 470, 827, 1274, 3276, 4204, 5134, 7559, 12676, 14898, 18123, 18819, 25690, 26459, 41628, 51387, 71783, 80330, 85687, 88171, 97063, 123630, 155930, 164987, 234760, 414840, 584995, 702038, 727699, 992700, 1201046, 1232255, 2312734, 3136255, 4235414, 6090515, 11484018, 11731850, 11895718, ... (sequence A002235 in the OEIS)

The primes for n≥234760 were found by the distributed computing project 321 search.[5] The largest of these, 3·211895718−1, has 3580969 digits and was found in June 2015.

In 2008, Primegrid took over the search for Thabit primes.[6] It is still searching and has already found all currently known Thabit primes with n ≥ 4235414.[7] It is also searching for primes of the form 3·2n+1, such primes are called Thabit primes of the second kind or 321 primes of the second kind.

The first few Thabit numbers of the second kind are:

4, 7, 13, 25, 49, 97, 193, 385, 769, 1537, 3073, 6145, 12289, 24577, 49153, 98305, 196609, 393217, 786433, 1572865, ... (sequence A181565 in the OEIS)

The first few Thabit primes of the second kind are:

7, 13, 97, 193, 769, 12289, 786433, 3221225473, 206158430209, 6597069766657, 221360928884514619393, ... (sequence A039687 in the OEIS)

Their n values are:

1, 2, 5, 6, 8, 12, 18, 30, 36, 41, 66, 189, 201, 209, 276, 353, 408, 438, 534, 2208, 2816, 3168, 3189, 3912, 20909, 34350, 42294, 42665, 44685, 48150, 54792, 55182, 59973, 80190, 157169, 213321, 303093, 362765, 382449, 709968, 801978, 916773, 1832496, 2145353, 2291610, 2478785, 5082306, 7033641, 10829346, ... (sequence A002253 in the OEIS)

Connection with amicable numbers

When both n and n−1 yield Thabit primes (of the first kind), and is also prime, a pair of amicable numbers can be calculated as follows:

and

For example, n = 2 gives the Thabit prime 11, and n−1 = 1 gives the Thabit prime 5, and our third term is 71. Then, 22=4, multiplied by 5 and 11 results in 220, whose divisors add up to 284, and 4 times 71 is 284, whose divisors add up to 220.

The only known n satisfying these conditions are 2, 4 and 7, corresponding to the Thabit primes 11, 47 and 383 given by n, the Thabit primes 5, 23 and 191 given by n−1, and our third terms are 71, 1151 and 73727. (The corresponding amicable pairs are (220, 284), (17296, 18416) and (9363584, 9437056))

Generalization

For integer b ≥ 2, a Thabit number base b is a number of the form (b+1)·bn − 1 for a non-negative integer n. Also, for integer b ≥ 2, a Thabit number of the second kind base b is a number of the form (b+1)·bn + 1 for a non-negative integer n.

The Williams numbers are also a generalization of Thabit numbers. For integer b ≥ 2, a Williams number base b is a number of the form (b−1)·bn − 1 for a non-negative integer n.[8] Also, for integer b ≥ 2, a Williams number of the second kind base b is a number of the form (b−1)·bn + 1 for a non-negative integer n.

For integer b ≥ 2, a Thabit prime base b is a Thabit number base b that is also prime. Similarly, for integer b ≥ 2, a Williams prime base b is a Williams number base b that is also prime.

Every prime p is a Thabit prime of the first kind base p, a Williams prime of the first kind base p+2, and a Williams prime of the second kind base p; if p ≥ 5, then p is also a Thabit prime of the second kind base p−2.

It is a conjecture that for every integer b ≥ 2, there are infinitely many Thabit primes of the first kind base b, infinitely many Williams primes of the first kind base b, and infinitely many Williams primes of the second kind base b; also, for every integer b ≥ 2 that is not congruent to 1 modulo 3, there are infinitely many Thabit primes of the second kind base b. (If the base b is congruent to 1 modulo 3, then all Thabit numbers of the second kind base b are divisible by 3 (and greater than 3, since b ≥ 2), so there are no Thabit primes of the second kind base b.)

The exponent of Thabit primes of the second kind cannot congruent to 1 mod 3 (except 1 itself), the exponent of Williams primes of the first kind cannot congruent to 4 mod 6, and the exponent of Williams primes of the second kind cannot congruent to 1 mod 6 (except 1 itself), since the corresponding polynomial to b is a reducible polynomial. (If n ≡ 1 mod 3, then (b+1)·bn + 1 is divisible by b2 + b + 1; if n ≡ 4 mod 6, then (b−1)·bn − 1 is divisible by b2b + 1; and if n ≡ 1 mod 6, then (b−1)·bn + 1 is divisible by b2b + 1) Otherwise, the corresponding polynomial to b is an irreducible polynomial, so if Bunyakovsky conjecture is true, then there are infinitely many bases b such that the corresponding number (for fixed exponent n satisfying the condition) is prime. ((b+1)·bn − 1 is irreducible for all nonnegative integer n, so if Bunyakovsky conjecture is true, then there are infinitely many bases b such that the corresponding number (for fixed exponent n) is prime)

b numbers n such that (b+1)·bn − 1 is prime
(Thabit primes of the first kind base b)
numbers n such that (b+1)·bn + 1 is prime
(Thabit primes of the second kind base b)
numbers n such that (b−1)·bn − 1 is prime
(Williams primes of the first kind base b)
numbers n such that (b−1)·bn + 1 is prime
(Williams primes of the second kind base b)
2 OEISA002235 OEISA002253 OEISA000043 0, 1, 2, 4, 8, 16, ... (see Fermat prime)
3 OEISA005540 OEISA005537 OEISA003307 OEISA003306
4 1, 2, 4, 5, 6, 7, 9, 16, 24, 27, 36, 74, 92, 124, 135, 137, 210, ... (none) OEISA272057 1, 3, 4, 6, 9, 15, 18, 33, 138, 204, 219, 267, ...
5 OEISA257790 OEISA143279 OEISA046865 OEISA204322
6 1, 2, 3, 13, 21, 28, 30, 32, 36, 48, 52, 76, ... 1, 6, 17, 38, 50, 80, 207, 236, 264, ... OEISA079906 OEISA247260
7 0, 4, 7, 10, 14, 23, 59, ... (none) OEISA046866 OEISA245241
8 1, 5, 7, 21, 33, 53, 103, ... 1, 2, 11, 14, 21, 27, 54, 122, 221, ... OEISA268061 OEISA269544
9 1, 2, 4, 5, 7, 10, 11, 13, 15, 19, 27, 29, 35, 42, 51, 70, 112, 164, 179, 180, 242, ... 0, 2, 6, 9, 11, 51, 56, 81, ... OEISA268356 OEISA056799
10 OEISA111391 (none) OEISA056725 OEISA056797
11 0, 1, 2, 3, 4, 11, 13, 22, 27, 48, 51, 103, 147, 280, ... 0, 2, 3, 6, 8, 138, 149, 222, ... OEISA046867 OEISA057462
12 2, 6, 11, 66, 196, ... 1, 2, 8, 9, 17, 26, 62, 86, 152, ... OEISA079907 OEISA251259

Least k ≥ 1 such that (n+1)·nk − 1 is prime are: (start with n = 2)

1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 2, 1, 2, 1, 1, 4, 3, 1, 1, 1, 2, 7, 1, 2, 1, 2, 1, 2, 1, 1, 2, 4, 2, 1, 2, 2, 1, 1, 2, 1, 8, 3, 1, 1, 1, 2, 1, 2, 1, 5, 3, 1, 1, 1, 1, 3, 3, 1, 1, 5, 2, 1483, 1, 1, 1, 24, 1, 2, 1, 2, 6, 3, 3, 36, 1, 10, 8, 3, 7, 2, 2, 1, 2, 1, 1, 7, 1704, 1, 3, 9, 4, 1, 1, 2, 1, 2, 24, 25, 1, ...

Least k ≥ 1 such that (n+1)·nk + 1 is prime are: (start with n = 2, 0 if no such k exists)

1, 1, 0, 1, 1, 0, 1, 2, 0, 2, 1, 0, 1, 1, 0, 1, 9, 0, 1, 1, 0, 2, 1, 0, 2, 1, 0, 5, 2, 0, 5, 1, 0, 2, 3, 0, 1, 3, 0, 1, 2, 0, 2, 2, 0, 2, 6, 0, 1, 183, 0, 2, 1, 0, 2, 1, 0, 1, 21, 0, 1, 185, 0, 3, 1, 0, 2, 1, 0, 1, 120, 0, 2, 1, 0, 1, 1, 0, 1, 8, 0, 5, 9, 0, 2, 2, 0, 1, 1, 0, 2, 3, 0, 9, 14, 0, 3, 1, 0, ...

Least k ≥ 1 such that (n−1)·nk − 1 is prime are: (start with n = 2)

2, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 2, 1, 14, 1, 1, 2, 6, 1, 1, 1, 55, 12, 1, 133, 1, 20, 1, 2, 1, 1, 2, 15, 3, 1, 7, 136211, 1, 1, 7, 1, 7, 7, 1, 1, 1, 2, 1, 25, 1, 5, 3, 1, 1, 1, 1, 2, 3, 1, 1, 899, 3, 11, 1, 1, 1, 63, 1, 13, 1, 25, 8, 3, 2, 7, 1, 44, 2, 11, 3, 81, 21495, 1, 2, 1, 1, 3, 25, 1, 519, 77, 476, 1, 1, 2, 1, 4983, 2, 2, ...

Least k ≥ 1 such that (n−1)·nk + 1 is prime are: (start with n = 2)

1, 1, 1, 2, 1, 1, 2, 1, 3, 10, 3, 1, 2, 1, 1, 4, 1, 29, 14, 1, 1, 14, 2, 1, 2, 4, 1, 2, 4, 5, 12, 2, 1, 2, 2, 9, 16, 1, 2, 80, 1, 2, 4, 2, 3, 16, 2, 2, 2, 1, 15, 960, 15, 1, 4, 3, 1, 14, 1, 6, 20, 1, 3, 946, 6, 1, 18, 10, 1, 4, 1, 5, 42, 4, 1, 828, 1, 1, 2, 1, 12, 2, 6, 4, 30, 3, 3022, 2, 1, 1, 8, 2, 4, 4, 2, 11, 8, 2, 1, ...

References

  1. ^ Rashed, Roshdi (1994). The development of Arabic mathematics: between arithmetic and algebra. 156. Dordrecht, Boston, London: Kluwer Academic Publishers. p. 277. ISBN 0-7923-2565-6.
  2. ^ [1]
  3. ^ [2]
  4. ^ [3]
  5. ^ [4]
  6. ^ [5]
  7. ^ [6]
  8. ^ List of Williams primes (of the first kind) base 3 to 2049 (for exponent ≥ 1)

External links

This page was last edited on 30 August 2019, at 21:10
Basis of this page is in Wikipedia. Text is available under the CC BY-SA 3.0 Unported License. Non-text media are available under their specified licenses. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc. WIKI 2 is an independent company and has no affiliation with Wikimedia Foundation.