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 1-3 of 3 results.

A092874 Decimal expansion of the "binary" Liouville number.

Original entry on oeis.org

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

Views

Author

Ferenc Adorjan (fadorjan(AT)freemail.hu)

Keywords

Comments

The famous Liouville number is defined so that its n-th fractional decimal digit is 1 if and only if there exists k, such that k! = n.
The binary Liouville number is defined similarly, but as a binary number: its n-th fractional binary digit is 1 if and only if there exists k, such that k! = n.
According to the definitions introduced in A092855 and A051006, this number is "the binary mapping" of the sequence of factorials (A000142).
For the numerators of the partial sums of B(n) := Sum_{j=1..n} 1/j^(n!) see A145572. - Wolfdieter Lang, Apr 10 2024

Examples

			0.7656250596046447753906250000... = 1/2^1 + 1/2^2 + 1/2^6 + 1/2^24 + 1/2^120 + ...
		

References

  • Steven R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, 2003, Section 2.22, p. 172.

Crossrefs

Programs

  • Mathematica
    RealDigits[Sum[1/2^(n!), {n, Infinity}], 10, 105][[1]] (* Alonso del Arte, Dec 03 2012 *)
  • PARI
    { mt(v)= /*Returns the binary mapping of v monotonic sequence as a real in (0,1)*/
    local(a=0.0,p=1,l);l=matsize(v)[2];
    for(i=1,l,a+=2^(-v[i])); return(a)}
    
  • PARI
    suminf(n=2,2^-gamma(n)) \\ Charles R Greathouse IV, Jun 14 2020

Extensions

Offset corrected by Franklin T. Adams-Watters, Dec 14 2017

A317873 Number of digits in 2^(n!).

Original entry on oeis.org

1, 1, 1, 2, 8, 37, 217, 1518, 12138, 109238, 1092378, 12016155, 144193850, 1874520045, 26243280622, 393649209329, 6298387349264, 107072584937472, 1927306528874488, 36618824048615255, 732376480972305082, 15379906100418406713, 338357934209204947674
Offset: 0

Views

Author

Keywords

Comments

The old definition (which did not match the data) was "Number of digits in the numerators of partial sums for Liouville's constant, read as base-2 (binary) numbers (A145572)."

Crossrefs

Programs

  • Maple
    Digits := 900: # for n <= 300
    a := n -> ceil(exp(lnGAMMA(n + 1))*log10(2)):
    seq(a(n), n = 0..30);  # Peter Luschny, Apr 18 2024
  • Mathematica
    Array[ Floor[#! Log10@2 + 1] &, 22]

Formula

a(n) = A034887(n!).

Extensions

Better definition suggested by Martin Renner, Mar 24 2024
a(0)=1 prepended by Alois P. Heinz, Jul 27 2025

A145571 Numerators of partial sums for Liouville's constant.

Original entry on oeis.org

1, 11, 110001, 110001000000000000000001, 110001000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
Offset: 1

Views

Author

Wolfdieter Lang, Mar 06 2009

Keywords

Comments

The denominators are 10^(n!).
In a(n) the 1's appear at positions j!, j=1..n. Therefore Liouville's constant c:=Sum_{k>=1} 1/10^(k!) is the number 0.a(n) with n -> infinity.
Liouville's constant c is transcendental. See, e.g., the proof in the Rosenberger-Fine reference.
The number of digits of a(n) is n! = A000142(n). The number of 0s is 0 for n = 1 and 2, and Sum_{k=3..n} (z(n) - 1), for n >= 3, where z(n) = n! - (n-1)! = A001563(n-1). This number is n! - n, for n >= 1. - Wolfdieter Lang, Apr 09 2024

Examples

			a(2)=11 because c(2)=1/10 + 1/100 = 11/100.
a(6) has 1's at positions 1,2,6,24,120,720 (A000142, factorials) and 0's in between.
		

References

  • B. Fine and G. Rosenberger, Number theory: an introduction via the distribution of primes, Birkhäuser, Boston, Basel, Berlin, 2007. Th. 6.3.2.3., p. 286.

Crossrefs

Cf. A000142, A001563, A145572 (a(n) read as base 2 representation).

Programs

  • Mathematica
    Numerator[Accumulate[1/10^Range[6]!]] (* Paolo Xausa, Jun 25 2024 *)
    Block[{k = 0}, NestList[#*10^(++k*k!) + 1 &, 1, 5]] (* Paolo Xausa, Jun 26 2024 *)

Formula

a(n) = numerator(c(n)), with c(n):= Sum_{k=1..n} 1/10^(k!).
a(1) = 1, and a(n) = a(n-1)*10^(z(n)) + 1, for n >= 2, where z(n) = A001563(n-1) = n! - (n-1)! = (n-1)!*(n-1). - Wolfdieter Lang, Apr 09 2024 [Corrected by Paolo Xausa, Jun 26 2024 ]
Showing 1-3 of 3 results.