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.

A052434 Nearest integer to R(n) - pi(n), where R(x) is the Riemann prime counting function.

Original entry on oeis.org

1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, -1, 0, 0, 0, -1, 0, 0, 0, 0, 1, 0, 0, -1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, -1, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, -1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, -1, -1, -1, 0, 0, 0, -1, 0, 0, 0, -1, -1, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0
Offset: 2

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Author

Keywords

Comments

The Riemann prime counting function R(n) = Sum_{prime powers p^k <= n} 1/k = A096624(n)/A096625(n). - N. J. A. Sloane, Feb 07 2023

Examples

			a(13) = 0 because R(13) = 5.504 and pi(13) = 6.
		

Crossrefs

Programs

Extensions

Corrected 6 terms, a(2), a(7), a(10), a(13), a(20) and a(48). Each was made 1 larger. Also gave an example for a(13) and a program for computing a(n). - Harry J. Smith, Dec 31 2008

A096624 Numerators of the Riemann prime counting function.

Original entry on oeis.org

0, 1, 2, 5, 7, 7, 9, 29, 16, 16, 19, 19, 22, 22, 22, 91, 103, 103, 115, 115, 115, 115, 127, 127, 133, 133, 137, 137, 149, 149, 161, 817, 817, 817, 817, 817, 877, 877, 877, 877, 937, 937, 997, 997, 997, 997, 1057, 1057, 1087, 1087, 1087, 1087, 1147, 1147, 1147
Offset: 1

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Author

Eric W. Weisstein, Jul 01 2004

Keywords

Examples

			0, 1, 2, 5/2, 7/2, 7/2, 9/2, 29/6, 16/3, 16/3, 19/3, ...
		

References

  • Paulo Ribenboim, The Little Book of Bigger Primes, Springer-Verlag NY 2004. See p. 167.

Crossrefs

Cf. A096625.

Programs

  • Mathematica
    Table[Sum[PrimePi[x^(1/k)]/k, {k, Log2[x]}], {x, 100}] // Numerator (* Eric W. Weisstein, Jan 09 2019 *)
  • PARI
    a(n) = numerator(sum(k=1, n, if (p=isprimepower(k), 1/p))); \\ Michel Marcus, Jan 07 2019
    
  • PARI
    a(n) = numerator(sum(k=1, logint(n, 2), primepi(sqrtnint(n, k))/k)); \\ Daniel Suteu, Jan 07 2019

Formula

Let Sk{f(k)}= Sum_{k>=2}f(k), then the g.f. of A096624/A096625 can be written as
(1/1)*Sa{(x^a)/(1-x)} - (1/2)*Sa{ Sb{ (x^(a*b))/(1-x)}} + (1/3)*Sa{ Sb{ Sc{ (x^(a*b*c))/(1-x)}}} - (1/4)*Sa{ Sb{ Sc{ Sd{ (x^(a*b*c*d))/(1-x)}}}} + ... . - Mats Granvik, Apr 06 2011
a(n)/A096625(n) = Sum_{p prime <= n} HarmonicNumber(floor(log_p n)). - Ammar Khatab, Jan 25 2025

A096623 Decimal expansion of Integral_{t>=2} 1/(t*log(t)(t^2-1)) dt.

Original entry on oeis.org

1, 4, 0, 0, 1, 0, 1, 0, 1, 1, 4, 3, 2, 8, 6, 9, 2, 6, 6, 8, 6, 9, 1, 7, 3, 0, 5, 2, 3, 4, 2, 9, 9, 7, 3, 3, 1, 7, 7, 5, 2, 7, 9, 2, 8, 1, 2, 7, 0, 6, 5, 8, 2, 8, 9, 4, 8, 9, 4, 6, 8, 7, 4, 3, 1, 1, 3, 0, 4, 9, 1, 4, 9, 9, 5, 1, 6, 1, 3, 6, 1, 0, 2, 7, 6, 0, 2, 6, 5, 3, 2, 0, 6, 4, 8, 6, 6, 6, 9, 6, 3, 4, 3, 4, 5
Offset: 0

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Author

Eric W. Weisstein, Jul 01 2004

Keywords

Comments

Maximum value of the integral in the Riemann prime counting function.

Examples

			0.1400101011432869266869173052342997331775279281270658289489468743113049149...
		

References

  • John Derbyshire, Prime Obsession, Joseph Henry Press, 2003, pp. 328-329.
  • Bernhard Riemann, On the Number of Prime Numbers less than a Given Quantity, 1859.

Crossrefs

Programs

  • Maple
    evalf(Integrate(1/(x*log(x)*(x^2-1)), x = 2..infinity), 120); # Vaclav Kotesovec, Feb 13 2019
  • Mathematica
    RealDigits[ NIntegrate[1/(t Log[t](t^2 - 1)), {t, 2, Infinity}, MaxRecursion -> 8, AccuracyGoal -> 115, WorkingPrecision -> 128]][[1]] (* Robert G. Wilson v, Jul 05 2004 *)
  • PARI
    default(realprecision, 120); intnum(x=2, oo, 1/(x*log(x)*(x^2 - 1))) \\ Vaclav Kotesovec, Feb 13 2019

A322714 a(n) = denominator of the Riemann prime counting function for 10^n.

Original entry on oeis.org

1, 3, 15, 2520, 45045, 102960, 232792560, 5354228880, 1115464350, 291136195350, 20629078984800, 144403552893600, 5342931457063200, 856326196254765600, 9419588158802421600, 3099044504245996706400, 4106233968125945635980, 16424935872503782543920
Offset: 0

Views

Author

Daniel Suteu, Dec 24 2018

Keywords

Examples

			0, 16/3, 428/15, 445273/2520, 56175529/45045, 991892879/102960, 18296822833013/232792560, ...
		

Crossrefs

The corresponding numerators are A322713.

Programs

  • PARI
    a(n) = denominator(sum(k=1, logint(10^n, 2), primepi(sqrtnint(10^n, k))/k));

Formula

a(n) = A096625(10^n).
a(n) = denominator of Sum_{k=1..floor(log_2(10^n))} pi(floor(10^(n/k)))/k, where pi(x) is the prime counting function A000720.
Showing 1-4 of 4 results.