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 1-4 of 4 results.

A133788 Primes where the record gaps in A053686 first appear.

Original entry on oeis.org

3, 7, 23, 113, 1327, 9551, 19609, 155921, 1357201, 4652353, 387096133, 3842610773
Offset: 1

Views

Author

N. J. A. Sloane, Dec 31 2007

Keywords

Extensions

a(4)-a(11) from Farideh Firoozbakht, Dec 31 2007
a(12) from Donovan Johnson, Nov 24 2008

A053695 Differences between record prime gaps.

Original entry on oeis.org

1, 2, 2, 2, 6, 4, 2, 2, 12, 2, 8, 8, 20, 14, 10, 16, 2, 4, 14, 16, 6, 26, 30, 10, 2, 12, 14, 2, 32, 6, 4, 28, 16, 18, 28, 2, 10, 62, 8, 4, 6, 12, 4, 10, 14, 2, 16, 2, 6, 42, 6, 14, 50, 22, 42, 50, 12, 26, 2, 100, 10, 8, 208, 52, 14, 22, 4, 24, 24, 56, 28, 14, 72, 34, 12, 22
Offset: 1

Views

Author

Jeff Burch, Mar 23 2000

Keywords

Comments

The largest known term of this sequence is a(63) = 1132 - 924 = 208. This seems rather strange for a(63) > 2*100+7 where 100 = max {a(k)| k < 63}. {1,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,42,50,52,56,62,72,100,208} is the set of the distinct first 75 terms of the sequence. What is the smallest number m such that a(m) = 36? - Farideh Firoozbakht, May 30 2014
Conjecture: a(n) <= A005250(n). Based on the equivalent statement at A005250: A005250(n+1) / A005250(n) <= 2. - John W. Nicholson, Dec 30 2015

Crossrefs

Programs

  • Mathematica
    m = 2; r = 0; Differences@ Reap[Monitor[Do[If[Set[d, Set[n, NextPrime[m]] - m] > r, Set[r, d]; Sow[d]]; m = n, {i, 10^7}], i]][[-1, -1]] (* Michael De Vlieger, Oct 30 2021 *)

Formula

a(n) = A005250(n+1) - A005250(n).
A005250(n+1) = 1 + Sum_{i=1..n} a(i). - John W. Nicholson, Dec 29 2015

Extensions

Missing term 1 and more terms added by Farideh Firoozbakht, May 30 2014
a(75)-a(76) from John W. Nicholson, Feb 27 2018

A085237 Nondecreasing gaps between primes.

Original entry on oeis.org

1, 2, 2, 4, 4, 4, 6, 6, 6, 6, 6, 6, 6, 8, 14, 14, 14, 18, 20, 22, 34, 34, 36, 36, 36, 44, 52, 52, 72, 86, 86, 96, 112, 114, 118, 132, 132, 148, 154, 154, 154, 180, 210, 220, 222, 234, 248, 250, 250, 282, 288, 292, 320, 336, 336, 354, 382, 384, 394, 456, 464, 468, 474, 486, 490, 500, 514, 516, 532, 534, 540, 582, 588, 602, 652, 674, 716, 766, 778
Offset: 1

Views

Author

Farideh Firoozbakht, Aug 11 2003

Keywords

Comments

All terms of A005250 are in the sequence, but some terms of A005250 appear in this sequence more than once.
a(n) is the gap between the n-th and (n+1)-th sublists of prime numbers defined in A348178. - Ya-Ping Lu, Oct 19 2021

Examples

			a(21) = a(22) = 34 because prime(218) - prime(217) = prime(1060) - prime(1059) = 34 and prime(n+1) - prime(n) is less than 34, for n < 1059 and n not equal to 217.
		

References

  • R. K. Guy, Unsolved problems in number theory.

Crossrefs

Programs

  • Mathematica
    f[n_] := Prime[n+1]-Prime[n]; v={}; Do[ If[f[n]>=If[n==1, 1, v[[ -1]]], v1=n; v=Append[v, f[v1]]; Print[v]], {n, 105000000}]
    DeleteDuplicates[Differences[Prime[Range[10^7]]],Greater] (* Harvey P. Dale, Jan 17 2024 *)
  • Python
    from sympy import nextprime; p, r = 2, 0
    while r < 778:
        q = nextprime(p); g = q - p
        if g >= r: print(g, end = ', '); r = g
        p = q # Ya-Ping Lu, Jan 23 2024

Extensions

a(53)-a(63) from Donovan Johnson, Nov 24 2008
a(64)-a(76) from Charles R Greathouse IV, May 09 2011
a(77)-a(79) from Charles R Greathouse IV, May 19 2011

A121069 Conjectured sequence for jumping champions greater than 1 (most common prime gaps up to x, for some x).

Original entry on oeis.org

2, 4, 6, 30, 210, 2310, 30030, 510510, 9699690, 223092870, 6469693230, 200560490130, 7420738134810, 304250263527210, 13082761331670030, 614889782588491410, 32589158477190044730, 1922760350154212639070
Offset: 1

Views

Author

Lekraj Beedassy, Aug 10 2006

Keywords

Comments

If n > 2, then a(n) = product of n-1 consecutive distinct prime divisors. E.g. a(5)=210, the product of 4 consecutive and distinct prime divisors, 2,3,5,7. - Enoch Haga, Dec 08 2007
From Bill McEachen, Jul 10 2022: (Start)
Rather than have code merely generating the conjectured values, one can compare values of sequence terms at the same position n. Specifically, locate new maximums where (p,p+even) are both prime, where even=2,4,6,8,... and the datum set is taken with even=4. A new maximum implies a new jumping champion.
Doing this produces the terms 2,4,6,30,210,2310,30030,.... Looking at the plot of a(n) ratio for gap=2/gap=6, the value changes VERY slowly, and is 2.14 after 50 million terms (one can see the trend via Plot 2 of A001359 vs A023201 (3rd option seqA/seqB vs n). The ratio for gap=4/gap=2 ~ 1, implying they are equally frequent. (End)

Crossrefs

Programs

  • Mathematica
    2,4,Table[Product[Prime[k],{k,1,n-1}],{n,3,30}]
  • PARI
    print1("2, 4");t=2;forprime(p=3,97,print1(", ",t*=p)) \\ Charles R Greathouse IV, Jun 11 2011

Formula

Consists of 4 and the primorials (A002110).
a(1) = 2, a(2) = 4, a(3) = 6, a(n+1)/a(n) = Prime[n] for n>2.

Extensions

Corrected and extended by Alexander Adamchuk, Aug 11 2006
Definition corrected and clarified by Jonathan Sondow, Aug 16 2011
Showing 1-4 of 4 results.