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 1-5 of 5 results.

A082838 Decimal expansion of Kempner series Sum_{k>=1, k has no digit 9 in base 10} 1/k.

Original entry on oeis.org

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

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Author

Robert G. Wilson v, Apr 14 2003

Keywords

Comments

Numbers with a digit 9 (A011539) have asymptotic density 1, i.e., here almost all terms are removed from the harmonic series, which makes convergence less surprising. See A082839 (the analog for digit 0) for more information about such so-called Kempner series. - M. F. Hasler, Jan 13 2020

Examples

			22.920676619264150348163657094375931914944762436998481568541998356... - _Robert G. Wilson v_, Jun 01 2009
		

References

  • Julian Havil, Gamma, Exploring Euler's Constant, Princeton University Press, Princeton and Oxford, 2003, page 34.

Crossrefs

Cf. A002387, A007095 (numbers with no '9'), A011539 (numbers with a '9'), A024101.
Cf. A082830 .. A082839 (analog for digits 1, ..., 8 and 0), A140502.

Programs

  • Mathematica
    (* see the Mmca in Wolfram Library Archive link *)

Formula

Equals Sum_{k in A007095\{0}} 1/k, where A007095 = numbers with no digit 9. - M. F. Hasler, Jan 15 2020

Extensions

More terms from Robert G. Wilson v, Apr 14 2009
More terms from Robert G. Wilson v, Jun 01 2009
Minor edits by M. F. Hasler, Jan 13 2020

A043525 Numbers having one 9 in base 10.

Original entry on oeis.org

9, 19, 29, 39, 49, 59, 69, 79, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 109, 119, 129, 139, 149, 159, 169, 179, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 209, 219, 229, 239, 249, 259, 269, 279, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 309, 319
Offset: 1

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Author

Keywords

Crossrefs

Programs

  • Mathematica
    Select[Range[300],DigitCount[#,10,9]==1&] (* Harvey P. Dale, Jan 19 2013 *)
  • Python
    def ok(n): return str(n).count('9') == 1
    print(list(filter(ok, range(320)))) # Michael S. Branicky, Sep 19 2021

Formula

Sum_{n>=1} 1/a(n) = A140502. - Amiram Eldar, Nov 14 2020

A179951 Decimal expansion of Sum_{k has exactly two bits equal to 1 in base 2} 1/k.

Original entry on oeis.org

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

Views

Author

Robert G. Wilson v, Aug 03 2010

Keywords

Comments

Obviously for k > 0 in base 2 having no bit equal to 1 the sum is 0 and for 1 bit equal to 1 the sum is 2.

Examples

			Sum_{k>0} 1/A018900(k) = 1.52899956069688841838263949451...
		

Crossrefs

Programs

  • Maple
     evalf( 2*add( (-1)^(n+1)*((4^n + 1)/(4^n - 1))*(1/2)^(n^2), n = 1..18), 100); # Peter Bala, Jan 28 2022
  • Mathematica
    (* first install irwinSums.m, see either reference, then *) First@ RealDigits@ iSum[1, 2, 2^7, 2]

Formula

Equals Sum_{j>=1} Sum_{i=0..j-1} 1/(2^i + 2^j).
From Amiram Eldar, Jun 30 2020: (Start)
Equals Sum_{k>=0} 1/(2^k + 1/2).
Equals 2 * A323482 - 1. (End)
Equals 2*Sum_{n >= 1} (-1)^(n+1)*((4^n + 1)/(4^n - 1))*(1/2)^(n^2). The first 18 terms of the series gives the constant correct to more than 100 decimal places. - Peter Bala, Jan 28 2022

A160502 Decimal expansion of the (finite) value of Sum_{ k >= 1, k has only a single zero digit in base 2 } 1/k.

Original entry on oeis.org

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

Views

Author

Robert G. Wilson v, May 15 2009

Keywords

Comments

The sum of 1/n where n has a single 0 in base 2.

Examples

			1.4625907350443646995461454467205346210747448647488211093642006243545229...
		

Crossrefs

Cf. A030130 (numbers with a single zero in base 2), A140502.

Programs

  • Mathematica
    RealDigits[ N[ Sum[1/(2^n - 1 - 2^k), {n, 2, 400}, {k, 0, n - 2}], 111]][[1]]
    (* first install irwinSums.m, see reference, then *) First@ RealDigits@ iSum[0, 1, 111, 2] (* Robert G. Wilson v, Aug 03 2010 *)

Formula

Equals Sum_{n>=2} Sum_{k=0..n-2}, 1/(2^n - 1 - 2^k).

A179954 Decimal expansion of the sum of the reciprocals of pandigital numbers in which each digit appears exactly once.

Original entry on oeis.org

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

Views

Author

Robert G. Wilson v, Aug 03 2010

Keywords

Comments

This is example in 3. 1(a) of R. Baillie, revised.
This is a finite sum so it is a rational number.

Examples

			0.0008258903479192529386079577501789135432537929965887385729771528345968177...
		

Crossrefs

Formula

Sum_{k=1..3265920} 1/A050278(k).

Extensions

Standardized offset and leading zeros from R. J. Mathar, Aug 06 2010
More terms from Robert G. Wilson v, Sep 07 2010
Showing 1-5 of 5 results.