cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-8 of 8 results.

A334544 Primes of the form 6k - 1 preceding the first-occurrence gaps in A334543.

Original entry on oeis.org

5, 29, 113, 197, 359, 521, 1109, 1733, 4289, 6389, 7349, 8297, 9059, 12821, 35603, 37691, 58787, 59771, 97673, 105767, 130649, 148517, 153749, 180797, 220019, 328127, 402593, 406907, 416693, 542261, 780401, 1138127, 1294367, 1444271, 1463621, 1604753
Offset: 1

Views

Author

Alexei Kourbatov, May 05 2020

Keywords

Comments

Subsequence of A007528. Contains A268929 as a subsequence. First differs from A268929 at a(5)=359.
A334543 lists the corresponding gap sizes; see more comments there.

Examples

			The first two primes of the form 6k-1 are 5 and 11; we have a(1)=5. The next primes of this form are 17, 23, 29; the gaps 17-11 = 23-17 = 29-23 have size 6 which already occurred before; so nothing is added to the sequence. The next prime of this form is 41 and the gap size 41-29=12 has not occurred before, so a(2)=29.
		

Crossrefs

Programs

  • PARI
    isFirstOcc=vector(9999,j,1); s=5; forprime(p=11,1e8,if(p%6!=5,next); g=p-s; if(isFirstOcc[g/6], print1(s", "); isFirstOcc[g/6]=0); s=p)

Formula

a(n) = A334545(n) - A334543(n).

A334545 Primes of the form 6k - 1 at the end of first-occurrence gaps in A334543.

Original entry on oeis.org

11, 41, 131, 227, 383, 557, 1151, 1787, 4337, 6449, 7433, 8363, 9137, 12893, 35729, 37781, 58889, 59879, 97787, 105863, 130769, 148667, 153887, 180959, 220151, 328271, 402761, 407153, 416849, 542441, 780587, 1138367, 1294571, 1444463, 1463837, 1604951
Offset: 1

Views

Author

Alexei Kourbatov, May 05 2020

Keywords

Comments

Subsequence of A007528. Contains A268930 as a subsequence. First differs from A268930 at a(5)=383.
A334543 lists the corresponding gap sizes; see more comments there.

Examples

			The first two primes of the form 6k-1 are 5 and 11, so we have a(1)=11. The next primes of this form are 17, 23, 29; the gaps 17-11 = 23-17 = 29-23 have size 6 which already occurred before; so nothing is added to the sequence. The next prime of this form is 41 and the gap size 41-29=12 has not occurred before, so a(2)=41.
		

Crossrefs

Programs

  • PARI
    isFirstOcc=vector(9999,j,1); s=5; forprime(p=11,1e8,if(p%6!=5,next); g=p-s; if(isFirstOcc[g/6], print1(p", "); isFirstOcc[g/6]=0); s=p)

Formula

a(n) = A334543(n) + A334544(n).

A014320 The next new gap between successive primes.

Original entry on oeis.org

1, 2, 4, 6, 8, 14, 10, 12, 18, 20, 22, 34, 24, 16, 26, 28, 30, 32, 36, 44, 42, 40, 52, 48, 38, 72, 50, 62, 54, 60, 58, 46, 56, 64, 68, 86, 66, 70, 78, 76, 82, 96, 112, 100, 74, 90, 84, 114, 80, 88, 98, 92, 106, 94, 118, 132, 104, 102, 110, 126, 120, 148, 108, 122, 138
Offset: 1

Views

Author

Hynek Mlcousek (hynek(AT)dior.ics.muni.cz)

Keywords

Comments

Prime differences A001223 in natural order with duplicates removed. - Reinhard Zumkeller, Apr 03 2015
Conjecture: a(n) = O(n). See arXiv:2002.02115 for discussion. - Alexei Kourbatov, Jun 04 2020

Examples

			The first two primes are 2 and 3, and the first prime gap is 3 - 2 = 1; so a(1) = 1. The next prime is 5, and the next gap is 5 - 3 = 2; this gap size has not occurred before, so a(2) = 2. The next prime is 7, and the next gap is 7 - 5 = 2; the gap size 2 has already occurred before, so nothing is added to the sequence.
		

Crossrefs

Programs

  • Haskell
    import Data.List (nub)
    a014320 n = a014320_list !! (n-1)
    a014320_list = nub $ a001223_list
    -- Reinhard Zumkeller, Apr 03 2015
    
  • Mathematica
    max = 300000; allGaps = Transpose[ {gaps = Differences[ Prime[ Range[max]]], Range[ Length[gaps]]}]; equalGaps = Split[ Sort[ allGaps, #1[[1]] < #2[[1]] & ], #1[[1]] == #2[[1]] & ]; firstGaps = ((Sort[#1, #1[[1]] < #2[[1]] & ] & ) /@ equalGaps)[[All, 1]]; Sort[ firstGaps, #1[[2]] < #2[[2]] & ][[All, 1]] (* Jean-François Alcover, Oct 21 2011 *)
    DeleteDuplicates[Differences[Prime[Range[10000]]]] (* Alonso del Arte, Jun 05 2020 *)
  • PARI
    my(isFirstOcc=vector(9999, j, 1), s=2); forprime(p=3, 1e8, my(g=p-s); if(isFirstOcc[g], print1(g, ", "); isFirstOcc[g]=0); s=p) \\ Alexei Kourbatov, Jun 03 2020
    
  • Scala
    val prime: LazyList[Int] = 2 #:: LazyList.from(3).filter(i => prime.takeWhile {
       j => j * j <= i
    }.forall {
       k => i % k != 0
    })
    val primes = prime.take(1000).toList
    primes.zip(primes.tail).map(p => p.2 - p._1).distinct // _Alonso del Arte, Jun 04 2020

Formula

a(n) = A335367(n) - A335366(n). - Alexei Kourbatov, Jun 04 2020
a(n) = 2*A014321(n-1) for n >= 2. - Robert Israel, May 27 2024

Extensions

More terms from Sascha Kurz, Mar 24 2002

A268928 Record (maximal) gaps between primes of the form 6k - 1.

Original entry on oeis.org

6, 12, 18, 30, 36, 42, 54, 60, 84, 126, 150, 162, 168, 246, 258, 318, 342, 354, 372, 408, 468, 534, 552, 600, 654, 762, 768, 798, 864, 894, 942, 960, 1068, 1224, 1302, 1320, 1344
Offset: 1

Views

Author

Alexei Kourbatov, Feb 15 2016

Keywords

Comments

Dirichlet's theorem on arithmetic progressions and the GRH suggest that average gaps between primes of the form 6k - 1 below x are about phi(6)*log(x). This sequence shows that the record gap ending at p grows almost as fast as phi(6)*log^2(p). Here phi(n) is A000010, Euler's totient function; phi(6)=2.
Conjecture: a(n) < phi(6)*log^2(A268930(n)) almost always.
Conjecture: phi(6)*n^2/6 < a(n) < phi(6)*n^2 almost always. - Alexei Kourbatov, Nov 27 2019

Examples

			The first two primes of the form 6k-1 are 5 and 11, so a(1)=11-5=6. The next primes of this form are 17, 23, 29; the gaps 17-11 = 23-17 = 29-23 are not records so nothing is added to the sequence. The next prime of this form is 41 and the gap 41-29=12 is a new record, so a(2)=12.
		

Crossrefs

Cf. A007528, A268929 (primes preceding the maximal gaps), A268930 (primes at the end of the maximal gaps), A334543, A334544.

Programs

  • Mathematica
    re = 0; s = 5; Reap[For[p = 11, p < 10^8, p = NextPrime[p], If[Mod[p, 6] != 5, Continue[]]; g = p - s; If[g > re, re = g; Print[g]; Sow[g]]; s = p]][[2, 1]] (* Jean-François Alcover, Dec 12 2018, from PARI *)
  • PARI
    re=0; s=5; forprime(p=11, 1e8, if(p%6!=5, next); g=p-s; if(g>re, re=g; print1(g", ")); s=p)

Formula

a(n) = A268930(n) - A268929(n). - Alexei Kourbatov, Jun 15 2020.

Extensions

Terms a(31)..a(37) from Alexei Kourbatov, Jun 15 2020

A268929 Primes 6k - 1 preceding the maximal gaps in A268928.

Original entry on oeis.org

5, 29, 113, 197, 521, 1109, 1733, 6389, 7349, 35603, 148517, 180797, 402593, 406907, 2339039, 5521721, 11157989, 20831267, 22440701, 27681263, 73451723, 241563407, 953758109, 1444257671, 1917281213, 6822753629, 15867286361, 28265029631, 40841579819, 177858259463
Offset: 1

Views

Author

Alexei Kourbatov, Feb 15 2016

Keywords

Comments

Subsequence of A007528 and A334544.
A268928 lists the corresponding record gap sizes. See more comments there.

Examples

			The first two primes of the form 6k-1 are 5 and 11, so a(1)=5. The next primes of this form are 17, 23, 29; the gaps 17-11 = 23-17 = 29-23 are not records so nothing is added to the sequence. The next prime of this form is 41 and the gap 41-29=12 is a new record, so a(2)=29.
		

Crossrefs

Programs

  • PARI
    re=0; s=5; forprime(p=11, 1e8, if(p%6!=5, next); g=p-s; if(g>re, re=g; print1(s", ")); s=p)

Formula

a(n) = A268930(n) - A268928(n). - Alexei Kourbatov, Jun 15 2020.

A268930 Primes 6k - 1 at the end of the maximal gaps in A268928.

Original entry on oeis.org

11, 41, 131, 227, 557, 1151, 1787, 6449, 7433, 35729, 148667, 180959, 402761, 407153, 2339297, 5522039, 11158331, 20831621, 22441073, 27681671, 73452191, 241563941, 953758661, 1444258271, 1917281867, 6822754391, 15867287129, 28265030429, 40841580683, 177858260357
Offset: 1

Views

Author

Alexei Kourbatov, Feb 15 2016

Keywords

Comments

Subsequence of A007528 and A334545.
A268928 lists the corresponding record gap sizes. See more comments there.

Examples

			The first two primes of the form 6k-1 are 5 and 11, so a(1)=11. The next primes of this form are 17, 23, 29; the gaps 17-11 = 23-17 = 29-23 are not records so nothing is added to the sequence. The next prime of this form is 41 and the gap 41-29=12 is a new record, so a(2)=41.
		

Crossrefs

Programs

  • PARI
    re=0; s=5; forprime(p=11, 1e8, if(p%6!=5, next); g=p-s; if(g>re, re=g; print1(p", ")); s=p)

Formula

a(n) = A268928(n) + A268929(n). - Alexei Kourbatov, Jun 15 2020.

A335366 Primes preceding the first-occurrence gaps in A014320.

Original entry on oeis.org

2, 3, 7, 23, 89, 113, 139, 199, 523, 887, 1129, 1327, 1669, 1831, 2477, 2971, 4297, 5591, 9551, 15683, 16141, 19333, 19609, 28229, 30593, 31397, 31907, 34061, 35617, 43331, 44293, 81463, 82073, 89689, 134513, 155921, 162143, 173359, 188029, 212701, 265621
Offset: 1

Views

Author

Alexei Kourbatov, Jun 03 2020

Keywords

Comments

Contains A002386 as a subsequence. First differs from A002386 at a(7)=139. This sequence is a permutation of all positive terms of A000230, in increasing order. See A002386 and A005250 for more references and links.

Examples

			The first two primes are 2 and 3, and the first prime gap is 3 - 2 = 1; so a(1)=2. The next prime is 5, and the next gap is 5 - 3 = 2; this gap size has not occurred before, so a(2)=3. The next prime is 7, and the next gap is 7 - 5 = 2; the gap size 2 has already occurred before, so nothing is added to the sequence.
		

Crossrefs

Programs

  • PARI
    my(isFirstOcc=vector(9999, j, 1), s=2); forprime(p=3, 1e8, my(g=p-s); if(isFirstOcc[g], print1(s, ", "); isFirstOcc[g]=0); s=p)

Formula

a(n) = A335367(n) - A014320(n).

A335367 Primes at the end of the first-occurrence gaps in A014320.

Original entry on oeis.org

3, 5, 11, 29, 97, 127, 149, 211, 541, 907, 1151, 1361, 1693, 1847, 2503, 2999, 4327, 5623, 9587, 15727, 16183, 19373, 19661, 28277, 30631, 31469, 31957, 34123, 35671, 43391, 44351, 81509, 82129, 89753, 134581, 156007, 162209, 173429, 188107, 212777, 265703
Offset: 1

Views

Author

Alexei Kourbatov, Jun 03 2020

Keywords

Comments

Contains A000101 as a subsequence. First differs from A000101 at a(7)=149. See A000101, A002386 and A005250 for more references and links.

Examples

			The first two primes are 2 and 3, and the first prime gap is 3 - 2 = 1; so a(1)=3. The next prime is 5, and the next gap is 5 - 3 = 2; this gap size has not occurred before, so a(2)=5. The next prime is 7, and the next gap is 7 - 5 = 2; the gap size 2 has already occurred before, so nothing is added to the sequence.
		

Crossrefs

Programs

  • PARI
    my(isFirstOcc=vector(9999, j, 1), s=2); forprime(p=3, 1e8, my(g=p-s); if(isFirstOcc[g], print1(p, ", "); isFirstOcc[g]=0); s=p)

Formula

a(n) = A335366(n) + A014320(n).
Showing 1-8 of 8 results.