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 1-10 of 43 results. Next

A154580 Decimal expansion of log_10 (15).

Original entry on oeis.org

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

Views

Author

N. J. A. Sloane, Oct 30 2009

Keywords

Examples

			1.1760912590556812420812890085306222824319389827285873235194...
		

Crossrefs

Cf. decimal expansion of log_10(m): A007524 (m=2), A114490 (m=3), A114493 (m=4), A153268 (m=5), A153496 (m=6), A153620 (m=7), A153790 (m=8), A104139 (m=9), A154182 (m=11), A154203 (m=12), A154368 (m=13), A154478 (m=14), this sequence, A154794 (m=16), A154860 (m=17), A154953 (m=18), A155062 (m=19), A155522 (m=20), A155677 (m=21), A155746 (m=22), A155830 (m=23), A155979 (m=24).

Programs

Formula

Equals A016638 / A002392 = (1+A152914)/(1+A152675). - R. J. Mathar, Jul 29 2024

A114493 Decimal expansion of log_10(4).

Original entry on oeis.org

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

Views

Author

Eric W. Weisstein, Dec 01 2005

Keywords

Comments

In engineering (all branches, but particularly electronic and electrical) power and amplitude ratios are measured rigorously in decibels (dB). This constant, with offset 1 (i.e., 6.02... = 10*A114493) is the dB equivalent of a 2:1 amplitude ratio or, equivalently, 4:1 power ratio. - Stanislav Sykora, Dec 11 2013

Examples

			0.602059991...
		

Crossrefs

Cf. decimal expansion of log_10(m): A007524 (m=2), A114490 (m=3), this sequence, A153268 (m=5), A153496 (m=6), A153620 (m=7), A153790 (m=8), A104139 (m=9), A154182 (m=11), A154203 (m=12), A154368 (m=13), A154478 (m=14), A154580 (m=15), A154794 (m=16), A154860 (m=17), A154953 (m=18), A155062 (m=19), A155522 (m=20), A155677 (m=21), A155746 (m=22), A155830 (m=23), A155979 (m=24).

Programs

Formula

A016627 divided by A002392. Two times A007524. - R. J. Mathar, Feb 21 2013
Equals 1/A154155. - R. J. Mathar, Jul 31 2025

A104139 Decimal expansion of log_10(9).

Original entry on oeis.org

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

Views

Author

Lekraj Beedassy, Mar 07 2005

Keywords

Examples

			log_10(9) = 0.95424250943932487459005580651...
		

Crossrefs

Cf. decimal expansion of log_10(m): A007524 (m = 2), A114490 (m = 3), A114493 (m = 4), A153268 (m = 5), A153496 (m = 6), A153620 (m = 7), A153790 (m = 8), this sequence, A154182 (m = 11), A154203 (m = 12), A154368 (m = 13), A154478 (m = 14), A154580 (m = 15), A154794 (m = 16), A154860 (m = 17), A154953 (m = 18), A155062 (m = 19), A155522 (m = 20), A155677 (m = 21), A155746 (m = 22), A155830 (m = 23), A155979 (m = 24).

Programs

Formula

Equals A016632 / A002392 . - R. J. Mathar, Mar 11 2008

Extensions

More terms from Stefan Steinerberger, Mar 14 2006
More terms from R. J. Mathar, Mar 11 2008

A154158 Decimal expansion of log_7(10).

Original entry on oeis.org

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

Views

Author

N. J. A. Sloane, Oct 30 2009

Keywords

Examples

			1.1832946624549383268179285616468591481654445229423947233563...
		

Crossrefs

Cf. decimal expansion of log_7(m): A152713 (m=2), A152945 (m=3), A153103 (m=4), A153203 (m=5), A153463 (m=6), A153755 (m=8), A113211 (m=9), this sequence, A154179 (m=11), A154200 (m=12), A154294 (m=13), A154467 (m=14), A154572 (m=15), A154793 (m=16), A154857 (m=17), A154912 (m=18), A155059 (m=19), A155496 (m=20), A155591 (m=21), A155735 (m=22), A155824 (m=23), A155964 (m=24).

Programs

  • Magma
    SetDefaultRealField(RealField(100)); Log(10)/Log(7); // G. C. Greubel, Sep 02 2018
  • Mathematica
    RealDigits[Log[7, 10], 10,100][[1]] (* Vincenzo Librandi, Aug 31 2013 *)
  • PARI
    default(realprecision, 100); log(10)/log(7) \\ G. C. Greubel, Sep 02 2018
    

Formula

Equals A002392 / A016630 = 1/A153620. - R. J. Mathar, Jul 31 2025

A083910 Number of divisors of n that are congruent to 0 modulo 10.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0
Offset: 1

Views

Author

Reinhard Zumkeller, May 08 2003

Keywords

Crossrefs

Programs

Formula

a(n) = A000005(n) - A083911(n) - A083912(n) - A083913(n) - A083914(n) - A083915(n) - A083916(n) - A083917(n) - A083918(n) - A083919(n).
a(10k) = tau(k) = A000005(k); a(n) = 0 if 10 does not divide n. - Franklin T. Adams-Watters, Apr 15 2007
G.f.: Sum_{k>=1} x^(10*k)/(1 - x^(10*k)). - Ilya Gutkovskiy, Sep 11 2019
Sum_{k=1..n} a(k) = n*log(n)/10 + c*n + O(n^(1/3)*log(n)), where c = (2*gamma - 1 - log(10))/10 = -0.214815..., and gamma is Euler's constant (A001620) (Smith and Subbarao, 1981). - Amiram Eldar, Dec 30 2023

A083911 Number of divisors of n that are congruent to 1 modulo 10.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 2, 2, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 2, 1, 1, 2
Offset: 1

Views

Author

Reinhard Zumkeller, May 08 2003

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := DivisorSum[n, 1 &, Mod[#, 10] == 1 &]; Array[a, 100] (* Amiram Eldar, Dec 30 2023 *)
  • PARI
    a(n) = sumdiv(n, d, d % 10 == 1); \\ Amiram Eldar, Dec 30 2023

Formula

a(n) = A000005(n) - A083910(n) - A083912(n) - A083913(n) - A083914(n) - A083915(n) - A083916(n) - A083917(n) - A083918(n) - A083919(n).
G.f.: Sum_{k>=1} x^k/(1 - x^(10*k)). - Ilya Gutkovskiy, Sep 11 2019
Sum_{k=1..n} a(k) = n*log(n)/10 + c*n + O(n^(1/3)*log(n)), where c = gamma(1,10) - (1 - gamma)/10 = 0.769838..., gamma(1,6) = -(psi(1/10) + log(10))/10 is a generalized Euler constant, and gamma is Euler's constant (A001620) (Smith and Subbarao, 1981). - Amiram Eldar, Dec 30 2023

A083913 Number of divisors of n that are congruent to 3 modulo 10.

Original entry on oeis.org

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

Views

Author

Reinhard Zumkeller, May 08 2003

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := DivisorSum[n, 1 &, Mod[#, 10] == 3 &]; Array[a, 100] (* Amiram Eldar, Dec 30 2023 *)
  • PARI
    a(n) = sumdiv(n, d, d % 10 == 3); \\ Amiram Eldar, Dec 30 2023

Formula

a(n) = A000005(n) - A083910(n) - A083911(n) - A083912(n) - A083914(n) - A083915(n) - A083916(n) - A083917(n) - A083918(n) - A083919(n).
G.f.: Sum_{k>=1} x^(3*k)/(1 - x^(10*k)). - Ilya Gutkovskiy, Sep 11 2019
Sum_{k=1..n} a(k) = n*log(n)/10 + c*n + O(n^(1/3)*log(n)), where c = gamma(3,10) - (1 - gamma)/10 = 0.07771547..., gamma(3,10) = -(psi(3/10) + log(10))/10 is a generalized Euler constant, and gamma is Euler's constant (A001620) (Smith and Subbarao, 1981). - Amiram Eldar, Dec 30 2023

A083917 Number of divisors of n that are congruent to 7 modulo 10.

Original entry on oeis.org

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

Views

Author

Reinhard Zumkeller, May 08 2003

Keywords

Crossrefs

Programs

Formula

a(n) = A000005(n) - A083910(n) - A083911(n) - A083912(n) - A083913(n) - A083914(n) - A083915(n) - A083916(n) - A083918(n) - A083919(n).
G.f.: Sum_{k>=1} x^(7*k)/(1 - x^(10*k)). - Ilya Gutkovskiy, Sep 11 2019
Sum_{k=1..n} a(k) = n*log(n)/10 + c*n + O(n^(1/3)*log(n)), where c = gamma(7,10) - (1 - gamma)/10 = -0.150534..., gamma(7,10) = -(psi(7/10) + log(10))/10 is a generalized Euler constant, and gamma is Euler's constant (A001620) (Smith and Subbarao, 1981). - Amiram Eldar, Dec 30 2023

A083919 Number of divisors of n that are congruent to 9 modulo 10.

Original entry on oeis.org

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

Views

Author

Reinhard Zumkeller, May 08 2003

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := DivisorSum[n, 1 &, Mod[#, 10] == 9 &]; Array[a, 100] (* Amiram Eldar, Dec 30 2023 *)
  • PARI
    a(n) = sumdiv(n, d, d % 10 == 9); \\ Amiram Eldar, Dec 30 2023

Formula

a(n) = A000005(n) - A083910(n) - A083911(n) - A083912(n) - A083913(n) - A083914(n) - A083915(n) - A083916(n) - A083917(n) - A083918(n).
G.f.: Sum_{k>=1} x^(9*k)/(1 - x^(10*k)). - Ilya Gutkovskiy, Sep 11 2019
Sum_{k=1..n} a(k) = n*log(n)/10 + c*n + O(n^(1/3)*log(n)), where c = gamma(9,10) - (1 - gamma)/10 = -0.197044..., gamma(9,10) = -(psi(9/10) + log(10))/10 is a generalized Euler constant, and gamma is Euler's constant (A001620) (Smith and Subbarao, 1981). - Amiram Eldar, Dec 30 2023

A002285 Decimal expansion of common logarithm of e.

Original entry on oeis.org

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

Views

Author

Keywords

Comments

Sometimes also called Briggs's constant after the English mathematician Henry Briggs (1561-1630). - Martin Renner, Jan 03 2022

Examples

			0.4342944819...
		

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.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • Jerome Spanier and Keith B. Oldham, "Atlas of Functions", Hemisphere Publishing Corp., 1987, chapter 25, equations 25:14:4 at page 232.
  • David Wells, The Penguin Dictionary of Curious and Interesting Numbers. Penguin Books, NY, 1986, Revised edition 1987, p. 27.

Crossrefs

Programs

Formula

Equals log_10(e) = 1/log(10) = 1/A002392. - Eric Desbiaux, Jun 27 2009
Conjecture by Eric Weisstein: Equals lim_{n->oo} b(n)/10^(n-1), for b=A114467 or b=A114468 (i.e., is the limit of the decimal expansion of the number of decimal digits in both the numerator and denominator of the (10^n)th harmonic number). More generally, log_k(e) seems to equal lim_{n->oo} floor(log_k(b(k^n)))/k^(n-1), for b=A001008 or b=A002805 and k >= 2. - Natalia L. Skirrow, Feb 12 2023
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