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 1-2 of 2 results.

A256319 Decimal expansion of Sum_{k>=0} (zeta(2k)/(2k+1))*(3/4)^(2k) (negated).

Original entry on oeis.org

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

Views

Author

Jean-François Alcover, Mar 23 2015

Keywords

Examples

			-0.0760998271297134006415132115417458357308529822614513901...
		

Crossrefs

Programs

  • Magma
    SetDefaultRealField(RealField(100)); R:=RealField(); Catalan(R)/(3*Pi(R)) - Log(2)/4; // G. C. Greubel, Aug 25 2018
  • Mathematica
    Join[{0}, RealDigits[Catalan/(3 Pi) - Log[2]/4, 10, 102] // First]
  • PARI
    suminf(k=0, (zeta(2*k)/(2*k+1))*(3/4)^(2*k)) \\ Michel Marcus, Mar 23 2015
    
  • PARI
    default(realprecision, 100); Catalan/(3*Pi) - log(2)/4 \\ G. C. Greubel, Aug 25 2018
    

Formula

Equals G/(3*Pi) - log(2)/4, where G is Catalan's constant.

A381028 Decimal expansion of Sum_{k>=1} zeta(2k)/((2k-1)*2^(2k)).

Original entry on oeis.org

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

Views

Author

R. J. Mathar, Feb 12 2025

Keywords

Comments

Including the term k=0 with zeta(0) = -1/2 gives 0.937658... = this + 1/2.

Examples

			0.4376582423112610933159209...
		

Crossrefs

Programs

  • Maple
    evalf(Sum(Zeta(2*k)/((2*k-1)*4^k), k = 1 .. infinity), 105) # Amiram Eldar, Feb 15 2025
  • Mathematica
    RealDigits[NSum[Zeta[2*k]/((2*k - 1)*4^k), {k, 1, Infinity}, WorkingPrecision -> 120, NSumTerms -> 200]][[1, 1 ;; 105]] (* Amiram Eldar, Feb 15 2025 *)
  • PARI
    sumpos(k=1, zeta(2*k)/((2*k-1)*2^(2*k))) \\ Michel Marcus, Feb 13 2025

Formula

4*this = 1.75063296924504437... = Sum_{k>=1} (1/k)*log((2k+1)/(2k-1)).
Equals Sum_{k>=1} arctanh(1/(2*k))/(2*k) = Sum_{k>=1} arccoth(2*k)/(2*k). - Amiram Eldar, Feb 15 2025

Extensions

More terms from Amiram Eldar, Feb 15 2025
Showing 1-2 of 2 results.