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.

A060199 Number of primes between n^3 and (n+1)^3.

Original entry on oeis.org

0, 4, 5, 9, 12, 17, 21, 29, 32, 39, 49, 52, 58, 73, 76, 88, 92, 109, 117, 125, 140, 151, 159, 176, 188, 199, 207, 233, 247, 254, 267, 284, 305, 320, 346, 338, 373, 385, 416, 418, 437, 458, 481, 504, 517, 551, 555, 583, 599, 636, 648, 678, 686, 733, 723, 753, 810
Offset: 0

Views

Author

Labos Elemer, Mar 19 2001

Keywords

Comments

Ingham showed that for n large enough and k=5/8, prime(n+1)-prime(n) = O(prime(n)^k). Ingham's result implies that there is a prime between sufficiently large consecutive cubes. Therefore a(n) is nonzero for n sufficiently large. Using the Riemann Hypothesis, Caldwell and Cheng prove there is a prime between all consecutive cubes. The question is undecided for squares. Many authors have reduced the value of k. The best value of k is 21/40, proved by Baker, Harman and Pintz in 2001. - corrected by Jonathan Sondow, May 19 2013
Conjecture: There are always more than 3 primes between two consecutive nonzero cubes. - Cino Hilliard, Jan 05 2003
Dudek (2014), correcting a claim of Cheng, shows that a(n) > 0 for n > exp(exp(33.217)) = 3.06144... * 10^115809481360808. - Charles R Greathouse IV, Jun 27 2014
Cully-Hugill shows the above for n > exp(exp(32.892)) = 6.92619... * 10^83675518094285. - Charles R Greathouse IV, Aug 02 2021
Mossinghoff, Trudgian, & Yang improve this to n > exp(exp(32.76)) = 3.62275 * 10^73328286790528. - Charles R Greathouse IV, Jul 31 2024

Examples

			n = 2: there are 5 primes between 8 and 27, 11,13,17,19,23.
n = 9, n+1 = 10: PrimePi(1000)-PrimePi(729) = 168-129 = a(9) = 39.
		

Crossrefs

First differences of A038098.

Programs

  • Magma
    [0] cat [#PrimesInInterval(n^3, (n+1)^3): n in [1..70]]; // Vincenzo Librandi, Feb 13 2016
    
  • Mathematica
    PrimePi[(#+1)^3]-PrimePi[#^3]&/@Range[0,60] (* Harvey P. Dale, Feb 08 2013 *)
    Last[#]-First[#]&/@Partition[PrimePi[Range[0,60]^3],2,1] (* Harvey P. Dale, Feb 02 2015 *)
  • PARI
    cubespr(n)= for(x=0,n, ct=0; for(y=x^3,(x+1)^3, if(isprime(y), ct++; )); if(ct>=0,print1(ct, ", ")))  \\ Cino Hilliard, Jan 05 2003
    
  • Python
    from sympy import primepi
    def a(n): return primepi((n+1)**3) - primepi(n**3)
    print([a(n) for n in range(57)]) # Michael S. Branicky, Jun 22 2021

Formula

Table[PrimePi[(j+1)^3]-PrimePi[j^3], {j, 1, 100}]

Extensions

Corrected and added more detail to the Ingham references. - T. D. Noe, Sep 23 2008
Combined two comments, correcting a bad error in the first comment. - T. D. Noe, Sep 27 2008
Edited by N. J. A. Sloane, Jan 17 2009 at the suggestion of R. J. Mathar

A086688 Number of primes < prime(n)^3.

Original entry on oeis.org

4, 9, 30, 68, 217, 327, 656, 882, 1457, 2707, 3228, 5194, 6850, 7789, 9916, 13746, 18411, 20179, 26062, 30597, 32984, 40991, 46959, 56924, 72217, 80725, 85182, 94695, 99669, 110127, 152280, 165951, 187910, 195660, 237427, 246434, 274614
Offset: 1

Views

Author

Cino Hilliard, Jul 28 2003

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := PrimePi[Prime[n]^3]; Array[a, 50] (* Amiram Eldar, Sep 06 2024 *)
  • PARI
    a(n) = primepi(prime(n)^3); \\ Michel Marcus, Sep 18 2023

Formula

a(n) = A038098(prime(n)). - R. J. Mathar, Sep 15 2012
a(n) = A000720(A030078(n)). - Michel Marcus, Sep 18 2023

A060304 Number of primes below n^3 does not exceed n times the number of primes below n^2.

Original entry on oeis.org

0, 0, 3, 6, 15, 19, 37, 47, 69, 82, 113, 139, 180, 216, 244, 300, 381, 423, 486, 553, 638, 726, 820, 887, 1029, 1152, 1256, 1376, 1527, 1659, 1794, 1992, 2156, 2357, 2517, 2739, 2909, 3085, 3365, 3627, 3933, 4200, 4380, 4687, 4960, 5313, 5547, 5917, 6395
Offset: 0

Views

Author

Labos Elemer, Mar 26 2001

Keywords

Examples

			n=10, 10*pi(100)=250, pi(1000)=168, a(10)=250-168=82.
		

Crossrefs

Programs

  • Mathematica
    Table[n*PrimePi[n^2]-PrimePi[n^3], {n, 1, 100}]

Formula

a(n) = n*pi(n*n) - pi(n*n*n). - Jonathan Sondow, Feb 17 2014
a(n) = n*A038107(n) - A038098(n). - Michel Marcus, Feb 17 2014

A365767 a(n) is the number of primes between (prime(n))^3 and (prime(n+1))^3.

Original entry on oeis.org

5, 21, 38, 149, 110, 329, 226, 575, 1250, 521, 1966, 1656, 939, 2127, 3830, 4665, 1768, 5883, 4535, 2387, 8007, 5968, 9965, 15293, 8508, 4457, 9513, 4974, 10458, 42153, 13671, 21959, 7750, 41767, 9007, 28180, 30226, 21322, 33813, 35899, 12506, 66241, 14003, 28809, 14848, 94735
Offset: 1

Views

Author

Zak Seidov and Robert Israel, Sep 18 2023

Keywords

Examples

			a(2) = 21 because there are 21 primes between prime(2)^3 = 27 and prime(3)^3 = 125.
		

Crossrefs

First differences of A086688.

Programs

  • Maple
    A:= [seq(numtheory:-pi(ithprime(i)^3),i=1..30)]:
    A[2..-1] - A[1..-2];

Formula

a(n) = A038098(A000040(n+1)) - A038098(A000040(n)).
Showing 1-4 of 4 results.