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 1-10 of 16 results. Next

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).

A131702 Distances between the locations of new prime gaps (A014320).

Original entry on oeis.org

0, 1, 4, 14, 5, 3, 11, 52, 54, 34, 27, 45, 18, 84, 61, 160, 147, 444, 647, 47, 311, 33, 851, 224, 82, 41, 216, 148, 728, 89, 3357, 57, 659, 3853, 1814, 504, 920, 1222, 2019, 4256
Offset: 1

Views

Author

Giovanni Teofilatto, Sep 16 2007

Keywords

Comments

A014320 lists "new" gaps in the sequence A001223 of prime gaps (not necessarily records as A005669 does).
The locations of these new gaps in A001223 are 1, 2, 4, 9, 24, 30, 34,...
The present sequence lists the first difference of these locations, minus 1: a(1) = 2-1-1. a(2)=4-2-1. a(3)=9-4-1. a(4)=24-9-1.
The sequence therefore argues: need to skip 0 in A001223 to reach a new gap, need to skip 1 to reach a new gap, need to skip 4 to reach a new gap...

Crossrefs

Cf. A001223.

Programs

  • Maple
    A001223 := proc(n) option remember; ithprime(n+1)-ithprime(n) ; end proc:
    A014320 := proc(n) option remember; if n = 1 then return 1; else for k from 1 do t := A001223(k) ; isn := true; for i from 1 to n-1 do if procname(i) = t then isn := false; end if; end do: if isn then return t; end if; end do: end if; end proc:
    locng := proc(n) option remember; g := A014320(n) ; for k from 1 do if A001223(k) = g then return k; end if; end do: end proc:
    A131702 := proc(n) locng(n+1)-locng(n)-1 ; end proc: seq(A131702(n),n=1..40) ;

Extensions

More terms, program and comment by R. J. Mathar, Aug 23 2010

A187779 Numbers n for which the terms of A014320 up to n=A014320(k) are a permutation of {1,2,4,6,...,2*(k-1)}.

Original entry on oeis.org

1, 2, 4, 6, 8, 12, 32, 36, 150
Offset: 1

Views

Author

Peter J. C. Moses, Jan 05 2013

Keywords

Comments

An old conjecture states that the equation prime(n+1)-prime(n)=2m is solvable for m=1/2,1,2,... . a(n) indicate the smallest term of A014320 such that among the previous terms there occur 1 and all previous even numbers<=a(n). The primes up to 10^8 do not generate any further terms.
According to Thomas R. Nicely (see Links) the next term, if it exists, must be greater than 1344 and equal to a gap occurring between primes greater than 4*10^18. - Giovanni Resta, Jan 06 2013

Crossrefs

Essentially equivalent to A179985.

Extensions

Definition corrected by Giovanni Resta, Jan 05 2013

A127480 A131702 and A014320 interleaved.

Original entry on oeis.org

0, 2, 1, 4, 4, 6, 14, 8, 5, 14, 3, 10, 11, 12, 52, 18, 54, 20, 34, 22, 27, 34, 45, 24, 18, 16, 84, 26, 61, 28, 160, 30, 147, 32, 444, 36, 647, 44, 47, 42, 311, 40, 33, 52, 851, 48, 224, 38, 82, 72, 41, 50, 216, 62, 148, 54, 728, 60, 89, 58
Offset: 1

Views

Author

Giovanni Teofilatto, Sep 12 2007

Keywords

Formula

a(2n)= A014320(n+1). a(2n-1) = A131702(n).

Extensions

Formulas added, sequence extended, arbitrarily defined first term replaced - R. J. Mathar, Aug 23 2010

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).

A058320 Distinct even prime-gap lengths (number of composites between primes), from 3+2, 7+4, 23+6,...

Original entry on oeis.org

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
Offset: 0

Views

Author

Warren D. Smith, Dec 11 2000

Keywords

Comments

Nicely and Nyman have sieved up to 1.3565*10^16 at least. They admit it is likely they have suffered from hardware or software bugs, but believe the probability the sequence up to this point is incorrect is <1 in a million. This sequence is presumably all even integers (in different order). It is not monotonic. The monotonic subsequence of record-breaking prime gaps is A005250.
Essentially the same as A014320. [From R. J. Mathar, Oct 13 2008]

Crossrefs

Equals 2*A014321(n-1).

Programs

  • Mathematica
    DeleteDuplicates[Differences[Prime[Range[2,200000]]]] (* Harvey P. Dale, Dec 07 2014 *)

Extensions

Comment corrected by Harvey P. Dale, Dec 07 2014

A334543 First occurrences of gaps between primes 6k - 1: gap sizes.

Original entry on oeis.org

6, 12, 18, 30, 24, 36, 42, 54, 48, 60, 84, 66, 78, 72, 126, 90, 102, 108, 114, 96, 120, 150, 138, 162, 132, 144, 168, 246, 156, 180, 186, 240, 204, 192, 216, 198, 210, 174, 258, 252, 222, 234, 228, 318, 282, 264, 276, 342, 306, 294, 312, 270, 354, 372
Offset: 1

Views

Author

Alexei Kourbatov, May 05 2020

Keywords

Comments

Contains A268928 as a subsequence. First differs from A268928 at a(5)=24.
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 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 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 41-29=12 has not occurred before, so a(2)=12.
		

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(g", "); isFirstOcc[g/6]=0); s=p)

Formula

a(n) = A334545(n) - A334544(n).

A330854 Primes of the form 6k + 1 preceding the first-occurrence gaps in A330853.

Original entry on oeis.org

7, 19, 43, 241, 283, 1327, 1489, 1951, 2389, 4363, 7789, 10177, 16759, 22189, 24247, 38461, 40237, 43441, 69499, 75403, 100801, 118927, 171271, 195541, 204163, 250279, 480169, 577639, 590437, 1164607, 1207699, 1278817, 1382221, 1467937, 1526659, 1889803, 2314369
Offset: 1

Views

Author

Alexei Kourbatov, Apr 27 2020

Keywords

Comments

Subsequence of A002476. First differs from A268926 in that that sequence does not include 283; all terms of A268926 are in this sequence but many terms of this sequence are not in A268926.

Examples

			The first two primes of the form 6k + 1 are 7 and 13, so a(1) = 7. The next prime of that form is 19, and the gap 19 - 13 = 6 already occurred; so a new term is not added to the sequence. The next prime of the form 6k + 1 is 31, and the gap 31 - 19 = 12 is occurring for the first time; therefore a(2) = 19.
The gap between 241 and the next prime of the form 6k + 1 (271) is 30. So 241 is in the sequence.
Although the gap between 283 and 307 is only 24 (which is less than 30), the gap is of a size not previously encountered. So 283 is in the sequence.
		

Crossrefs

Cf. A002476, A014320, A058320, A330853 (gap sizes), A330855.

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(s", "); isFirstOcc[g/6]=0); s=p)

Formula

a(n) = A330855(n) - A330853(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).
Showing 1-10 of 16 results. Next