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 1-3 of 3 results.

A027570 Initial members of prime decaplets (p, p+2, p+6, p+12, p+14, p+20, p+24, p+26, p+30, p+32).

Original entry on oeis.org

9853497737, 21956291867, 22741837817, 164444511587, 179590045487, 217999764107, 231255798857, 242360943257, 666413245007, 696391309697, 867132039857, 974275568237, 976136848847, 1002263588297, 1086344116367
Offset: 1

Views

Author

Keywords

Comments

All terms are congruent to 167 (modulo 210). - Matt C. Anderson, May 29 2015

Crossrefs

Programs

  • Maple
    a := 1:
    for b to 25 do
    a := a*ithprime(b):
    end do:
    a;
    # now 'a' is the product of the primes less than 100.
    composite_small := proc (n::integer)
    description "procedure to determine if n has a prime factor less than 100";
    if igcd(2305567963945518424753102147331756070, n) = 1 then return false
    else return true;
    end if;
    end proc:
    # so composite_small tests if there are any factors 2 through 97.
    #begin initialization section
    p := [0, 2, 6, 12, 14, 20, 24, 26, 30, 32];
    o := [7517, 10247, 12137, 14447, 14867, 17177, 21377, 24107, 25997, 28727];
    m := 30030;
    #end initialization section
    # implement isprime(m*n+o+p)
    with(ArrayTools):
    os:=Size(o,2):
    ps:=Size(p,2):
    #here ps is 10 so a prime constellation of length 10.
    loopstop := 10^11:
    loopstart := 0:
    for n from loopstart to loopstop do
    for a to os do
    counter := 0; wc := 0; wd := 0;
      while `and`(wd > -10, wd < ps) do
      wd := wd+1;
      if composite_small(m*n+o[a]+p[wd]) = false then wd := wd+1
      else wd := -10 end if;
      end do;
    if wd >= 9 then
    while `and`(counter >= 0, wc < ps) do
      wc := wc+1;
      if isprime(m*n+o[a]+p[wc]) then counter := counter+1;
      else counter := -1
      end if;
    end do;
    end if;
    if counter = ps then print(m*n+o[a]) end if;
    end do:
    end do:
    # Matt C. Anderson, Apr 15 2015
  • Perl
    use ntheory ":all"; say for sieve_prime_cluster(1,1e13, 2,6,12,14,20,24,26,30,32); # Dana Jacobsen, Sep 30 2015

A202361 Record (maximal) gaps between prime decuplets (p+0,2,6,12,14,20,24,26,30,32).

Original entry on oeis.org

12102794130, 141702673770, 424052301750, 699699330330, 714303547230, 739544215410, 1623198312120, 2691533434590, 4207848555330, 4936074819480, 5887574660310, 6562654104930, 7205070907650, 8129061524010, 8362548652500, 9741706748970, 9967327212570
Offset: 1

Views

Author

Alexei Kourbatov, Dec 18 2011

Keywords

Comments

Prime decuplets (p+0,2,6,12,14,20,24,26,30,32) are one of the two types of densest permissible constellations of 10 primes (A027569 and A027570).
Average gaps between prime k-tuples are O(log^k(p)), with k=10 for decuplets, by the Hardy-Littlewood k-tuple conjecture. If a gap is larger than any preceding gap, we call it a maximal gap, or a record gap. Maximal gaps may be significantly larger than average gaps; this sequence suggests that maximal gaps are O(log^11(p)).
A202362 lists initial primes in decuplets (p+0,2,6,12,14,20,24,26,30,32) preceding the maximal gaps.

Examples

			The gap of 12102794130 between the very first decuplets starting at p=9853497737 and p=21956291867 is the initial term a(1)=12102794130.
The next gap after the decuplet starting at p=21956291867 is smaller, so it is not in this sequence.
The next gap of 141702673770 between the decuplets at p=22741837817 and p=164444511587 is a new record; therefore the next term is a(2)=141702673770.
		

Crossrefs

Cf. A027570 (prime decuplets p+0,2,6,12,14,20,24,26,30,32), A202362, A113274, A113404, A200503, A201596, A201598, A201062, A201073, A201051, A201251, A202281.

Programs

Formula

(1) Upper bound: gaps between prime decuplets (p+0,2,6,12,14,20,24,26,30,32) are smaller than 0.00059*(log p)^11, where p is the prime at the end of the gap.
(2) Estimate for the actual size of maximal gaps near p: max gap = a(log(p/a)-0.2), where a = 0.00059*(log p)^10 is the average gap between 10-tuples near p.
Both formulas (1) and (2) are derived from the Hardy-Littlewood k-tuple conjecture via probability-based heuristics relating the expected maximal gap size to the average gap. Neither of the formulas has a rigorous proof.

A202282 Initial prime in prime decuplets (p+0,2,6,8,12,18,20,26,30,32) preceding the maximal gaps in A202281.

Original entry on oeis.org

11, 33081664151, 83122625471, 294920291201, 730121110331, 1291458592421, 4700094892301, 6218504101541, 7908189600581, 10527733922591, 21939572224301, 23960929422161, 30491978649941, 46950720918371, 84254447788781, 118565337622001, 124788318636251, 235474768767851
Offset: 1

Views

Author

Alexei Kourbatov, Dec 15 2011

Keywords

Comments

Prime decuplets (p+0,2,6,8,12,18,20,26,30,32) are one of the two types of densest permissible constellations of 10 primes. Maximal gaps between decuplets of this type are listed in A202281; see more comments there.

Examples

			The first four gaps (after the decuplets starting at p=11, 33081664151, 83122625471, 294920291201) form an increasing sequence, with the size of each gap setting a new record. Therefore these values of p are in the sequence, as a(1), a(2), a(3), a(4). The next gap is not a record, so the respective initial prime is not in the sequence.
		

Crossrefs

Cf. A027569 (prime decuplets p+0,2,6,8,12,18,20,26,30,32), A202281, A202361, A202362.

Programs

Showing 1-3 of 3 results.