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 1-7 of 7 results.

A330853 First occurrences of gaps between primes 6k+1: gap sizes.

Original entry on oeis.org

6, 12, 18, 30, 24, 54, 42, 36, 48, 60, 78, 66, 72, 84, 90, 96, 114, 102, 162, 108, 126, 120, 132, 150, 138, 144, 174, 168, 156, 192, 204, 180, 198, 252, 270, 216, 222, 186, 228, 210, 240, 282, 246, 234, 276, 264, 258, 312, 330, 318, 288, 306, 294, 336, 300, 378
Offset: 1

Views

Author

Alexei Kourbatov, Apr 27 2020

Keywords

Comments

Contains A268925 as a subsequence.
Conjecture: the sequence is a permutation of all positive multiples of 6, i.e., all positive terms of A008588.
Conjecture: a(n) = O(n). See arXiv:2002.02115 (sect.7) for discussion.

Examples

			The first primes of the form 6k+1 are 7 and 13, so a(1)=13-7=6. The next prime 6k+1 is 19, and the gap 19-13=6 already occurred, so a new term is not added to the sequence. The next prime 6k+1 is 31, and the gap 31-19=12 is occurring for the first time; therefore a(2)=12.
		

Crossrefs

Cf. A002476, A014320, A058320, A330854 (primes 6k+1 preceding the first-occurrence gaps), A330855 (primes 6k+1 at the end of the first-occurrence gaps).

Programs

  • PARI
    isFirstOcc=vector(9999,j,1); s=7; forprime(p=13,1e8, if(p%6!=1,next); g=p-s; if(isFirstOcc[g/6], print1(g", "); isFirstOcc[g/6]=0); s=p)

Formula

a(n) = A330855(n) - A330854(n).

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).

A330855 Primes 6k + 1 at the end of first-occurrence gaps in A330853.

Original entry on oeis.org

13, 31, 61, 271, 307, 1381, 1531, 1987, 2437, 4423, 7867, 10243, 16831, 22273, 24337, 38557, 40351, 43543, 69661, 75511, 100927, 119047, 171403, 195691, 204301, 250423, 480343, 577807, 590593, 1164799, 1207903, 1278997, 1382419, 1468189, 1526929, 1890019, 2314591
Offset: 1

Views

Author

Alexei Kourbatov, Apr 27 2020

Keywords

Comments

Subsequence of A002476. Contains A268927 as a subsequence. First differs from A268927 at a(5)=307.
A330853 lists the corresponding gap sizes; see more comments there.

Examples

			The first two primes of the form 6k+1 are 7 and 13, so a(1)=13. The next prime 6k+1 is 19, and the gap 19-13=6 already occurred, so a new term is not added to the sequence. The next prime 6k+1 is 31, and the gap 31-19=12 is occurring for the first time; therefore a(2)=31.
		

Crossrefs

Cf. A002476, A014320, A058320, A268927, A330853 (first-occurrence gap sizes), A330854 (primes beginning the first-occurrence gaps).

Programs

  • PARI
    isFirstOcc=vector(9999,j,1); s=7; forprime(p=13,1e8, if(p%6!=1,next); g=p-s; if(isFirstOcc[g/6], print1(p", "); isFirstOcc[g/6]=0); s=p)

Formula

a(n) = A330853(n) + A330854(n).

A268925 Record (maximal) gaps between primes of the form 6k + 1.

Original entry on oeis.org

6, 12, 18, 30, 54, 60, 78, 84, 90, 96, 114, 162, 174, 192, 204, 252, 270, 282, 312, 330, 336, 378, 462, 486, 522, 528, 534, 600, 606, 612, 642, 666, 780, 810, 894, 1002
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(A268927(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 7 and 13, so a(1)=13-7=6. The next prime of this form is 19; the gap 19-13 is not a record so nothing is added to the sequence. The next prime of this form is 31; the gap 31-19=12 is a new record, so a(2)=12.
		

Crossrefs

Cf. A002476, A268926 (primes preceding the maximal gaps), A268927 (primes at the end of maximal gaps), A330853, A330854.

Programs

  • Mathematica
    re = 0; s = 7; Reap[For[p = 13, p < 10^8, p = NextPrime[p], If[Mod[p, 6] != 1, 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 *)
    records[n_]:=Module[{ri=n,m=0,rcs={},len},len=Length[ri];While[len>0,If[ First[ri]>m,m=First[ri];AppendTo[rcs,m]];ri=Rest[ri];len--]; rcs]; records[ Differences[Select[6*Range[0,3*10^6]+1,PrimeQ]]] (* the program generates the first 30 terms of the sequence. *) (* Harvey P. Dale, Dec 19 2021 *)
  • PARI
    re=0; s=7; forprime(p=13, 1e8, if(p%6!=1, next); g=p-s; if(g>re, re=g; print1(g", ")); s=p)

Formula

a(n) = A268927(n) - A268926(n). - Alexei Kourbatov, Jun 21 2020

A268926 Primes 6k + 1 preceding the maximal gaps in A268925.

Original entry on oeis.org

7, 19, 43, 241, 1327, 4363, 7789, 22189, 24247, 38461, 40237, 69499, 480169, 1164607, 1207699, 1467937, 1526659, 3975721, 11962651, 14466637, 19097257, 30097861, 39895309, 198389311, 303644227, 393202123, 485949253, 680676109, 1917214927, 3868900621, 4899889741, 6957509653, 7599382573
Offset: 1

Views

Author

Alexei Kourbatov, Feb 15 2016

Keywords

Comments

Subsequence of A002476 and A330854.
A268925 lists the corresponding record gap sizes. See more comments there.

Examples

			The first two primes of the form 6k+1 are 7 and 13, so a(1)=7. The next prime of this form is 19; the gap 19-13 is not a record so nothing is added to the sequence. The next prime of this form is 31 and the gap 31-19=12 is a new record, so a(2)=19.
		

Crossrefs

Programs

  • PARI
    re=0; s=7; forprime(p=13, 1e8, if(p%6!=1, next); g=p-s; if(g>re, re=g; print1(s", ")); s=p)

Formula

a(n) = A268927(n) - A268925(n). - Alexei Kourbatov, Jun 21 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 1-7 of 7 results.