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.

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A256843 Decimal expansion of the generalized Euler constant gamma(2,3).

Original entry on oeis.org

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

Views

Author

Jean-François Alcover, Apr 11 2015

Keywords

Examples

			0.07320737570615959366903185990752913907462383026830934562939...
		

Crossrefs

Cf. A001620 (gamma(1,1) = EulerGamma), A002391, A200064.
Primitive ruler-and-compass constructible gamma(r,k): A228725 (1,2), A256425 (1,3), A256778 (1,4), A256779 (1,5), A256780 (2,5), A256781 (1,8), A256782 (3,8), A256783 (1,12), A256784 (5,12).
Other gamma(r,k) (1 <= r <= k <= 5): A239097 (2,2), A256843 (2,3), A256844 (3,3), A256845 (2,4), A256846 (3,4), A256847 (4,4), A256848 (3,5), A256849 (4,5), A256850 (5,5).

Programs

  • Magma
    SetDefaultRealField(RealField(100)); R:= RealField(); EulerGamma(R)/3 - Pi(R)/(6*Sqrt(3)) + Log(3)/6; // G. C. Greubel, Aug 28 2018
  • Mathematica
    Join[{0}, RealDigits[-Log[3]/3 - PolyGamma[2/3]/3, 10, 105] // First]
  • PARI
    default(realprecision, 100); Euler/3 - Pi/(6*sqrt(3)) + log(3)/6 \\ G. C. Greubel, Aug 28 2018
    

Formula

Equals EulerGamma/3 - Pi/(6*sqrt(3)) + log(3)/6.
Equals -(psi(2/3) + log(3))/3 = (A200064 - A002391)/3. - Amiram Eldar, Jan 07 2024

A016578 Decimal expansion of log(3/2).

Original entry on oeis.org

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

Views

Author

Keywords

Examples

			0.4054651081081643819780131154643491365719904234624941976140143...
		

References

  • L. B. W. Jolley, Summation of Series, Dover (1961), eq (102), page 20.

Crossrefs

Programs

  • Mathematica
    RealDigits[Log[3/2],10,111][[1]] (* Robert G. Wilson v, Aug 08 2011 *)
  • PARI
    default(realprecision, 20080); x=10*log(3/2); for (n=0, 20000, d=floor(x); x=(x-d)*10; write("b016578.txt", n, " ", d)); \\ Harry J. Smith, May 17 2009

Formula

Equals Sum {k>=1} 1/(k*3^k). - Robert G. Wilson v, Aug 08 2011
Equals 1/2 - 1/(2*2^2) + 1/(3*2^3) - 1/(4*2^4) + ... [Jolley].
Equals A002391-A002162. - Michel Marcus, Sep 17 2016
From Amiram Eldar, Aug 07 2020: (Start)
Equals 2 * arctanh(1/5).
Equals Integral_{x=0..oo} 1/(2*exp(x) + 1) dx. (End)
log(3/2) = 2*Sum_{n >= 1} 1/(n*P(n, 5)*P(n-1, 5)), where P(n, x) denotes the n-th Legendre polynomial. The first 10 terms of the series gives the approximation log(3/2) = 0.40546510810816438197(04...), correct to 20 decimal places. - Peter Bala, Mar 16 2024
Equals Sum_{n >= 1} (-1)^(n+1) * 5/(n*binomial(2*n, n)*6^n). The n-th term of the series is O(5*sqrt(Pi/n)*1/24^n). - Peter Bala, Mar 04 2025
Equals Integral_{x=0..1} (sqrt(x) - 1)/log(x) dx. - Kritsada Moomuang, Jun 14 2025

A304656 Decimal expansion of Pi*sqrt(3).

Original entry on oeis.org

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

Views

Author

Peter Luschny, May 16 2018

Keywords

Examples

			5.4413980927026535517822347729264671968521987442782217267096548061643695433790...
		

Crossrefs

Programs

  • Maple
    Pi*sqrt(3): evalf(%, 100);
  • Mathematica
    RealDigits[N[StieltjesGamma[0,1/6]-StieltjesGamma[0,5/6],99]][[1]] (* corrected by Harvey P. Dale, Oct 13 2020 *)
    RealDigits[Pi Sqrt[3],10,120][[1]] (* Harvey P. Dale, Oct 13 2020 *)
  • Python
    # Use several guard digits when computing.
    # BBP formula (9/32) P(1, 64, 6, (16, 8, 0, -2, -1, 0)).
    from decimal import Decimal as dec, getcontext
    def BBPpisqrt3(n: int) -> dec:
        getcontext().prec = n
        s = dec(0); f = dec(1); g = dec(64)
        for k in range(int(n * 0.5536546824812272) + 1):
            sixk = dec(6 * k)
            s += f * ( dec(16) / (sixk + 1) + dec(8) / (sixk + 2)
                     - dec(2)  / (sixk + 4) - dec(1) / (sixk + 5) )
            f /= g
        return (s * dec(9)) / dec(32)
    print(BBPpisqrt3(200))  # Peter Luschny, Nov 03 2023

Formula

Equals gamma(0, 1/6) - gamma(0, 5/6) where gamma(n,x) denotes the generalized Stieltjes constants.
Equals PolyGamma[0, 5/6] - PolyGamma[0, 1/6].
Equals 3*sqrt(2*zeta(2)).
Pi^2 = A304656 * A093602.
From Amiram Eldar, Aug 06 2020: (Start)
Equals Sum_{k>=0} 1/((k + 1/3)*(k + 2/3)).
Equals Integral_{x=0..oo} log(1 + 3/x^2) dx. (End)
Equals (27*S - 36)/8, where S = A248682. - Peter Luschny, Jul 22 2022
From Peter Bala, Oct 26 2023: (Start)
sqrt(3)*Pi = 9/2 + 9*Sum_{n >= 1} (-1)^(n+1)/(9*n^2 - 1);
sqrt(3)*Pi = 5 + 10*Sum_{n >= 1} 1/((4*n^2 - 1)*(9*n^2 - 1)) = 43/8 + 8*Sum_{n >= 2} (-1)^n/((n^2 - 1)*(9*n^2 - 1));
sqrt(3)*Pi = 1765/324 - (80/9)*Sum_{n >= 2} 1/((n^2 - 1)*(4*n^2 - 1)*(9*n^2 - 1)).
The following two series representations for the constant
sqrt(3)*Pi = 72 * Sum_{n >= 0} (2*n + 1)/((6*n + 1)*(6*n + 3)*(6*n + 5)) and
sqrt(3)*Pi = 8192/1485 - 860160 * Sum_{n >= 0} (2*n + 3)/((6*n + 1)*(6*n + 3)*...*(6*n + 17)) appear to generalize as follows:
for k >= 0, sqrt(3)*Pi = c(k) + (-1)^k*d(k)*Sum_{n >= 0} (2*n + 2*k + 1)/((6*n + 1)*(6*n + 3)*...*(6*n + 12*k + 5)), where c(k) is a rational number approximating sqrt(3)*Pi and d(k) = (6*k + 1)! * 2^(6*k+3) / 3^(3*k-2).
The first few values of c(k) for k >= 0 are [0, 8192/1485, 11341398016/2085060285, 62809601736704/11542783997745, 889063287831973723111424/ 163388820474305231710905, ...].
The following two series representations for the constant
sqrt(3)*Pi = 256/45 - 2560*Sum_{n >= 0} 1/((6*n + 1)*(6*n + 3)*...*(6*n + 11)) and
sqrt(3)*Pi = 337117184/62026965 + 2018508800*Sum_{n >= 0} 1/((6*n + 1)*(6*n + 3)*...*(6*n + 23)) appear to generalize as follows:
for k >= 0, sqrt(3)*Pi = c(k) - (-1)^k*d(k)*Sum_{n >= 0} 1/((6*n + 1)*(6*n + 3)*...*(6*n + 12*k + 11)), where c(k) is a rational number approximating sqrt(3)*Pi and d(k) = (6*k + 5)! * 2^(6*k+6) / 3^(3*k+1).
The first few values of c(k) for k >= 0 are [256/45, 337117184/62026965, 1732370763874304/318357429615225, 733187044080753836032/134742553582636674675, 6361250411469779336874164224/1169047010493653932891525275, ...]. (End)
For arbitrary integer k, Pi*sqrt(3) = Sum_{n >= 0} (1/(n - k + 1/6) - 1/(n + k + 5/6)) = Sum_{n >= 0} (1/(n + k + 7/6) - 1/(n - k - 1/6)). - Peter Bala, Jul 10 2024

A016632 Decimal expansion of log(9).

Original entry on oeis.org

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

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Author

Keywords

Examples

			2.197224577336219382790490473845051409294981115645498903469388667274988...
		

References

  • M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 2.

Crossrefs

Cf. A016737 Continued fraction.

Programs

  • Mathematica
    First[RealDigits[Log[9], 10, 100]] (* Paolo Xausa, Mar 21 2024 *)
  • PARI
    default(realprecision, 20080); x=log(9); for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b016632.txt", n, " ", d)); \\ Harry J. Smith, May 16 2009

Formula

log(9) = 2*Sum_{n >= 1} 1/(n*P(n, 5/4)*P(n-1, 5/4)), where P(n, x) denotes the n-th Legendre polynomial. The first 20 terms of the series gives the approximation log(9) = 2.19722457733(34...), correct to 11 decimal places. - Peter Bala, Mar 18 2024
Equals 2*A002391. - R. J. Mathar, Jun 10 2024

A016635 Decimal expansion of log(12).

Original entry on oeis.org

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

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Author

Keywords

Examples

			2.484906649788000310229709479838878840798490826543259959976...
		

References

  • Milton Abramowitz and Irene A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 2.

Crossrefs

Cf. A016740 Continued fraction.

Programs

  • Mathematica
    RealDigits[Log[12], 10, 120][[1]] (* Alonso del Arte, Mar 12 2015 *)
  • PARI
    default(realprecision, 20080); x=log(12); for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b016635.txt", n, " ", d)); \\ Harry J. Smith, May 16 2009, corrected May 19 2009

Formula

Equals 2*A002162 + A002391. - R. J. Mathar, Jun 10 2024

A154920 Denominators of a ternary BBP-type formula for log(3).

Original entry on oeis.org

1, 18, 27, 324, 405, 4374, 5103, 52488, 59049, 590490, 649539, 6377292, 6908733, 66961566, 71744535, 688747536, 731794257, 6973568802, 7360989291, 69735688020, 73222472421, 690383311398, 721764371007, 6778308875544
Offset: 0

Views

Author

Jaume Oliver Lafont, Jan 17 2009, Jan 18 2009

Keywords

Comments

log(3) = Sum_{k>=0} (9/(2k+1)+1/(2k+2))/9^(k+1).
log(3) = 1 + Sum_{k>=0} (1/(2k+2)+1/(2k+3))/9^(k+1).

Crossrefs

Programs

Formula

a(n) = (n+1)*9^[(n+1)/2] = 18*a(n-2) - 81*a(n-4).
Sum_{n>=0} 1/a(n) = log(3).
G.f.: (1+18*x+9*x^2)/(1-9*x^2)^2. - Jaume Oliver Lafont, Jan 29 2009
a(n) = (2-(-1)^n)*(n+1)*3^n. - Jaume Oliver Lafont, Sep 27 2009
Sum_{n>=0} (-1)^n/a(n) = log(8/3). - Amiram Eldar, Feb 26 2022

A016650 Decimal expansion of log(27).

Original entry on oeis.org

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

Views

Author

Keywords

Examples

			3.295836866004329074185735710767577113942471673468248355204083000912482... - _Harry J. Smith_, May 20 2009
		

References

  • M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 2.

Crossrefs

Cf. A016455 (continued fraction).

Programs

  • Mathematica
    RealDigits[Log[27],10,120][[1]] (* Harvey P. Dale, May 07 2012 *)
  • PARI
    default(realprecision, 20080); x=log(27); for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b016650.txt", n, " ", d)); \\ Harry J. Smith, May 20 2009

Formula

Log(27) = Integral_{x = 0..oo} sin(4*x)^3/x^2 dx. - Peter Bala, Nov 04 2019
From Peter Bala, Feb 27 2024: (Start)
Equals 4 - 2*Sum_{k >= 0} 1/((2*k + 1)*(2*k + 3)*4^k).
Continued fraction: 4 - 16/(24 - 96/(84 - 1440/(186 - ... - 16*n*(n + 1)(4*n^2 - 1)/((2*(n + 1)*(10*n + 11)) - ... )))). (End)
Equals 3*A002391. - R. J. Mathar, Jul 22 2025

A097321 a(n) = (3*n-1) * 3*n * (3*n+1).

Original entry on oeis.org

24, 210, 720, 1716, 3360, 5814, 9240, 13800, 19656, 26970, 35904, 46620, 59280, 74046, 91080, 110544, 132600, 157410, 185136, 215940, 249984, 287430, 328440, 373176, 421800, 474474, 531360, 592620, 658416, 728910, 804264, 884640, 970200, 1061106, 1157520
Offset: 1

Views

Author

Ralf Stephan, Aug 07 2004

Keywords

Crossrefs

Programs

Formula

G.f.: 6x * (4x^2 + 19x + 4) / (1-x)^4.
Sum_{n>=1} 1/a(n) = (log(3) - 1)/2. - Amiram Eldar, Jul 04 2020
Sum_{n>=1} (-1)^(n+1)/a(n) = 1/2 - 2*log(2)/3. - Amiram Eldar, May 15 2022
E.g.f.: 3*exp(x)*x*(8 + 27*x + 9*x^2). - Stefano Spezia, Feb 20 2025

A256127 Decimal expansion of the second Malmsten integral: Integer_{x >= 1} log(log(x))/(1 + x + x^2) dx, negated.

Original entry on oeis.org

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

Views

Author

Keywords

Examples

			-0.12632148170620903636522675325320239184424430946528...
		

Crossrefs

Cf. A115252 (first Malmsten integral), A256128 (third Malmsten integral) , A256129 (fourth Malmsten integral), A073005 (Gamma(1/3)), A256165 (log(Gamma(1/3))), A061444 (log(2*Pi)), A002391 (log 3), A002194 (sqrt 3).

Programs

  • Maple
    evalf(Pi*(8*log(2*Pi) - 3*log(3) - 12*log(GAMMA(1/3)))/(6*sqrt(3)),120); # Vaclav Kotesovec, Mar 17 2015
  • Mathematica
    RealDigits[Integrate[Log[Log[1/x]]/(1 + x + x^2), {x, 0, 1}], 10, 100][[1]] (* Alonso del Arte, Mar 16 2015 *)
    RealDigits[Pi*(8*Log[2*Pi] - 3*Log[3] - 12*Log[Gamma[1/3]])/(6*Sqrt[3]),10,105][[1]] (* Vaclav Kotesovec, Mar 17 2015 *)
  • PARI
    Pi*(8*log(2*Pi) - 3*log(3) - 12*log(gamma(1/3)))/(6*sqrt(3)) \\ Michel Marcus, Mar 18 2015
    
  • PARI
    intnum(x=0, 1, log(log(1/x))/(1 + x + x^2))
    
  • PARI
    intnum(x=1, oo, log(log(x))/(1 + x + x^2))
    
  • PARI
    intnum(x=0, [oo, 1], log(x)/(1 + 2*cosh(x))) \\ Gheorghe Coserea, Sep 26 2018

Formula

Equals Integral_{x=0..1} log(log(1/x))/(1 + x + x^2) dx.
Equals Integral_{x>=0} log(x)/(1 + 2*cosh(x)) dx.
Equals Pi*(8*log(2*Pi) - 3*log(3) - 12*log(Gamma(1/3)))/(6*sqrt(3)).

A256128 Decimal expansion of the third Malmsten integral: int_{x=1..infinity} log(log(x))/(1 - x + x^2) dx, negated.

Original entry on oeis.org

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

Views

Author

Keywords

Examples

			-0.671719601885874542354405069288779884008802066219356...
		

Crossrefs

Cf. A115252 (first Malmsten integral), A256127 (second Malmsten integral), A256129 (fourth Malmsten integral), A073005 (Gamma(1/3)), A002162 (log 2), A002391 (log 3), A053510 (log Pi), A002194 (sqrt 3).

Programs

  • Maple
    evalf(Pi*(7*log(2)+8*log(Pi)-3*log(3)-12*log(GAMMA(1/3)))/(3*sqrt(3)),120); # Vaclav Kotesovec, Mar 17 2015
  • Mathematica
    RealDigits[Pi*(7*Log[2]+8*Log[Pi]-3*Log[3]-12*Log[Gamma[1/3]])/(3*Sqrt[3]),10,105][[1]] (* Vaclav Kotesovec, Mar 17 2015 *)
  • PARI
    Pi*(7*log(2)+8*log(Pi)-3*log(3)-12*log(gamma(1/3)))/(3*sqrt(3)) \\ Michel Marcus, Mar 18 2015

Formula

Equals integral_{x=0..1} log(log(1/x))/(1 - x + x^2) dx.
Equals integral_{x=0..infinity} log(x)/(1 - 2*cosh(x)) dx.
Equals Pi*(7*log(2) + 8*log(Pi) - 3*log(3) - 12*log(Gamma(1/3)))/(3*sqrt(3)).
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