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 16 results. Next

A365238 Decimal expansion of 1/A066716 (Binary Champernowne constant).

Original entry on oeis.org

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

Views

Author

Kelvin Voskuijl, Aug 27 2023

Keywords

Examples

			1.15976973235066807158695812033014828339074163177157159329786...
		

Crossrefs

Cf. A066716.

Programs

  • Mathematica
    RealDigits[1/ChampernowneNumber[2] , 10, 120][[1]]

A033308 Decimal expansion of Copeland-Erdős constant: concatenate primes.

Original entry on oeis.org

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

Views

Author

Keywords

Comments

The number .23571113171923.... was proved normal in base 10 by Copeland and Erdős but is not known to be normal in other bases. - Jeffrey Shallit, Mar 14 2008
Could be read (with indices 1, 2, ...) as irregular table whose n-th row lists the A097944(n) digits of the n-th prime A000040(n). - M. F. Hasler, Oct 25 2019
Named after the American mathematician Arthur Herbert Copeland (1898-1970) and the Hungarian mathematician Paul Erdős (1913-1996). - Amiram Eldar, May 29 2021
This constant is irrational but it is not (yet) known to be transcendental. - Charles R Greathouse IV, Feb 03 2025

Examples

			0.235711131719232931374143475359616771737983899710110310710911312...
		

References

  • Steven R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, 2003, Section 6.9, p. 442.
  • Glyn Harman, One hundred years of normal numbers, in M. A. Bennett et al., eds., Number Theory for the Millennium, II (Urbana, IL, 2000), A K Peters, Natick, MA, 2002, pp. 149-166.
  • Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 60.

Crossrefs

Cf. A030168 (continued fraction), A072754 (numerators of convergents), A072755 (denominators of convergents).
Cf. A000040 (primes), A097944 (row lengths if this is read as table), A228355 (digits of the primes listed in reversed order).
Cf. A033307 (Champernowne constant: analog for positive integers instead of primes), A007376 (digits of the integers, considered as infinite word or table), A066716 (decimals of the binary Champernowne constant).
Cf. A066747 and A191232: binary Copeland-Erdős constant: decimals and binary digits.
See also A338072.

Programs

  • Haskell
    a033308 n = a033308_list !! (n-1)
    a033308_list = concatMap (map (read . return) . show) a000040_list :: [Int]
    -- Reinhard Zumkeller, Mar 03 2014
  • Mathematica
    N[Sum[Prime[n]*10^-(n + Sum[Floor[Log[10, Prime[k]]], {k, 1, n}]), {n, 1, 40}], 100] (* Joseph Biberstine (jrbibers(AT)indiana.edu), Aug 12 2006 *)
    N[Sum[Prime@n*10^-(n + Sum[Floor[Log[10, Prime@k]], {k, n}]), {n, 45}], 106] (* Joseph Biberstine (jrbibers(AT)indiana.edu), Aug 12 2006 *)
    IntegerDigits //@ Prime@Range@45 // Flatten (* Robert G. Wilson v Oct 03 2006 *)
  • PARI
    default(realprecision, 2080); x=0.0; m=-1; forprime (p=2, 4000, n=1+floor(log(p)/log(10)); x=p+x*10^n; m+=n; ); x=x/10^m; for (n=0, 2000, d=floor(x); x=(x-d)*10; write("b033308.txt", n, " ", d)); \\ Harry J. Smith, Apr 30 2009
    
  • PARI
    concat( apply( {row(n)=digits(prime(n))},  [1..99] )) \\ Yields this sequence; row(n) then yields the digits of prime(n) = n-th row of the table, cf. comments. - M. F. Hasler, Oct 25 2019
    

Formula

Equals Sum_{n>=1} prime(n)*10^(-A068670(n)). - Joseph Biberstine (jrbibers(AT)indiana.edu), Aug 12 2006
Equals Sum_{i>=1} (p_i * 10^(-(Sum_{j=1..i} 1 + floor(log_10(p_j))) )) or Sum_{i>=1} (p_i * 10^(-( i + Sum_{j=1..i} floor(log_10(p_j))) )) or Sum_{i>=1} (p_i * 10^(-( Sum_{j=1..i} ceiling(log_10(1 + p_j))) )). - Daniel Forgues, Mar 26-28 2014

A047778 Concatenation of the first n numbers in binary (converted to base 10).

Original entry on oeis.org

1, 6, 27, 220, 1765, 14126, 113015, 1808248, 28931977, 462911642, 7406586283, 118505380540, 1896086088653, 30337377418462, 485398038695407, 15532737238253040, 497047591624097297, 15905522931971113522, 508976733823075632723, 16287255482338420247156
Offset: 1

Views

Author

Aaron Gulliver (gulliver(AT)elec.canterbury.ac.nz)

Keywords

Comments

The smallest prime in this sequence is 485398038695407. What is the full subsequence of primes? - N. J. A. Sloane, Oct 03 2015
There is only the one prime in the first 22400 terms, making a second prime > 10^91000. - Hans Havermann, Oct 07 2015

Examples

			a(4) = 1 10 11 100 [base 2] = 220 [base 10].
		

Crossrefs

Cf. A001855 (bit counts, offset by 1), A061168, A066716.
Concatenation of first n numbers in other bases: 2: this sequence, 3: A048435, 4: A048436, 5: A048437, 6: A048438, 7: A048439, 8: A048440, 9: A048441, 10: A007908, 11: A048442, 12: A048443, 13: A048444, 14: A048445, 15: A048446, 16: A048447.

Programs

  • Haskell
    a047778 = (foldl (\v d -> 2*v + d) 0) . concatMap (reverse . unfoldr
       (\x -> if x == 0 then Nothing else Just $ swap $ divMod x 2)) .
       enumFromTo 1
    -- Reinhard Zumkeller, Feb 19 2012
    
  • Maple
    conc:= (x,y) -> x*2^(1+ilog2(y))+y:
    a[1]:= 1:
    for n from 2 to 30 do a[n]:= conc(a[n-1],n) od:
    seq(a[n],n=1..30); # Robert Israel, Oct 07 2015
  • Mathematica
    If[STARTPOINT==1,n={},n=Flatten[IntegerDigits[Range[STARTPOINT-1],2]]]; Table[AppendTo[n,IntegerDigits[w,2]];n=Flatten[n];FromDigits[n,2],{w,STARTPOINT,ENDPOINT}] (* Dylan Hamilton, Aug 04 2010 *)
    f[n_] := FromDigits[ Flatten@ IntegerDigits[ Range@n, 2], 2]; Array[f, 18] (* Robert G. Wilson v, Nov 07 2010 *)
    Module[{n = 1}, NestList[#*2^BitLength[++n] + n &, 1, 25]] (* Paolo Xausa, Sep 30 2024 *)
  • PARI
    cb(a,b)=a<<#binary(b) + b
    a(n)=fold(cb, [1..n]) \\ Charles R Greathouse IV, Jun 21 2017
    
  • PARI
    A047778_vec(N=20,s)=vector(N,k,s=s<M. F. Hasler, Oct 25 2019
    
  • Python
    def a(n): return int("".join([(bin(i))[2:] for i in range(1, n+1)]), 2)
    print([a(n) for n in range(1, 19)]) # Michael S. Branicky, Jan 06 2021
    
  • Python
    from functools import reduce
    def A047778(n): return reduce(lambda i,j:(i<Chai Wah Wu, Feb 26 2023

Formula

a(n) = a(n-1)*2^(1+floor(log_2(n))) + n. - Henry Bottomley, Jan 12 2001
a(n) = 4C / 2^frac(log_2(n)) * n^{n+1} / r(frac(log_2(n)))^n + O(1), where r(x) = 2^{x - 1 + 2^{1-x}}; frac is the fractional part function frac(x) = x - floor(x); and C is the binary Champernowne constant (A066716). (In fact, a(n) is the floor of this expression; the error term is between 1/2 and 1.) r(x) takes on values between e*log(2) and 2 for x in the range 0 to 1. It follows using Stirling's approximation that the radius of convergence for the e.g.f. is log 2. - Franklin T. Adams-Watters, Sep 07 2006

Extensions

More terms from Patrick De Geest, May 15 1999
Name edited by Joe B. Stephen, Jul 22 2023

A066717 The continued fraction for the "binary" Champernowne constant.

Original entry on oeis.org

0, 1, 6, 3, 1, 6, 5, 3, 3, 1, 6, 4, 1, 3, 298, 1, 6, 1, 1, 3, 285, 7, 2, 4, 1, 2, 1, 2, 1, 1, 4534532, 1, 4, 5, 1, 2, 1, 7, 1, 16, 1, 4, 1, 5, 5, 1, 5, 1, 4, 1, 2, 1, 5, 3, 2, 38, 2, 12, 1, 15, 2, 6, 3, 30, 4682854730443938, 1, 1, 68, 1, 6, 5, 4, 4, 1, 2, 1, 1, 1, 1, 2, 22, 1, 2, 7, 1, 2
Offset: 0

Views

Author

Robert G. Wilson v, Jan 14 2002

Keywords

Crossrefs

Cf. A030190 & A066716 (binary & decimal digits of the binary Champernowne constant), A033307 (decimal Champernowne constant).
Cf. A054635, A077771, A077772: base 3, decimals and continued fraction of ternary Champernowne constant.

Programs

  • Mathematica
    a = {}; Do[a = Append[a, IntegerDigits[n, 2]], {n, 1, 10^3} ]; ContinuedFraction[ N[ FromDigits[ {Flatten[a], 0}, 2], 500]]
    almostNatural[n_, b_] :=  Block[{m = 0, d = n, i = 1, l, p}, While[m <= d, l = m; m = (b - 1) i*b^(i - 1) + l; i++]; i--; p = Mod[d - l, i]; q = Floor[(d - l)/i] + b^(i - 1); If[p != 0, IntegerDigits[q, b][[p]], Mod[q - 1, b]]]; Take[ ContinuedFraction[ FromDigits[ {Array[almostNatural[#, 2] &, 20000], 0}, 2]], 100] (* Robert G. Wilson v, Jul 21 2014 *)
  • PARI
    A066717(b=2,t=1.,s=b)={contfrac(sum(n=1,default(realprecision)*2.303\log(b)+1, nM. F. Hasler, Oct 25 2019

A077772 Continued fraction expansion of the ternary Champernowne constant.

Original entry on oeis.org

0, 1, 1, 2, 37, 1, 162, 1, 1, 1, 3, 1, 7, 1, 9, 2, 3, 1, 3068518062211324, 2, 1, 2, 6, 13, 1, 2, 1, 3, 1, 10, 1, 21, 1, 1, 4, 3, 577, 1, 1079268324684171943515797470873767312825026176345571319042096689270, 1, 1, 1, 3, 4, 21, 3, 1, 9, 1
Offset: 0

Views

Author

Eric W. Weisstein, Nov 15 2002

Keywords

Crossrefs

Cf. A054635 (ternary digits), A077771 (decimals).
Cf. A030190, A066716, A066717: binary digits, decimals and continued fraction of the binary Champernowne constant; A033307: decimal Champernowne constant.

Programs

  • Mathematica
    almostNatural[n_, b_] :=  Block[{m = 0, d = n, i = 1, l, p}, While[m <= d, l = m; m = (b - 1) i*b^(i - 1) + l; i++]; i--; p = Mod[d - l, i]; q = Floor[(d - l)/i] + b^(i - 1); If[p != 0, IntegerDigits[q, b][[p]], Mod[q - 1, b]]]; Take[ ContinuedFraction[ FromDigits[ {Array[almostNatural[#, 3] &, 20000], 0}, 3]], 100] (* Robert G. Wilson v, Jul 21 2014 *)
  • PARI
    \p 10000
    t=0;r=0.;T=1; for(n=1,1e6,d=#digits(n,3);t+=d;T*=3^d;r+=n/T;if(t>20959, return)); v=contfrac(r); v[1..30] \\ Charles R Greathouse IV, Sep 23 2014
    
  • PARI
    A077772(b=3,t=1.,s=b)={contfrac(sum(n=1,default(realprecision)*2.303/log(b)+1, nM. F. Hasler, Oct 25 2019

A058935 Concatenation of first n binary numbers.

Original entry on oeis.org

0, 1, 110, 11011, 11011100, 11011100101, 11011100101110, 11011100101110111, 110111001011101111000, 1101110010111011110001001, 11011100101110111100010011010, 110111001011101111000100110101011, 1101110010111011110001001101010111100
Offset: 0

Views

Author

Henry Bottomley, Jan 12 2001

Keywords

Comments

If the terms are read as decimal numbers, which of them are primes? For example, a(5) = 11011100101 = 1193*9229757 is not a prime. - N. J. A. Sloane, Feb 17 2023
Answer: a(231) is the first prime term when read as a decimal number; a(15) is the first when read as a binary number. - Michael S. Branicky, Feb 17 2023

Crossrefs

Cf. A047778 for this converted to decimal, A001855 (offset) for number of digits.
Cf. A066716: binary Champernowne constant, A030302: binary digits, A030190: same with initial 0, A030303: indices of 1's, A007088.
Other bases: A117640 (4), A007908 (10).

Programs

  • Mathematica
    FromDigits /@ Flatten /@ Rest[FoldList[Append, {}, IntegerDigits[Range[10], 2]]] (* Eric W. Weisstein, Nov 04 2015 *)
  • Python
    from itertools import count, islice
    def agen(s=""): yield from (int(s:=s+bin(n)[2:]) for n in count(0))
    print(list(islice(agen(), 13))) # Michael S. Branicky, Feb 17 2023
    
  • Python
    from functools import reduce
    def A058935(n): return int(bin(reduce(lambda i,j:(i<Chai Wah Wu, Feb 26 2023

Formula

a(n) = a(n-1)*10^A029837(n) + A007088(n).

A077771 Decimal value of the ternary Champernowne constant.

Original entry on oeis.org

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

Views

Author

Eric W. Weisstein, Nov 15 2002

Keywords

Comments

The first 99 digits form a prime. - Jonathan Vos Post, Nov 11 2004
This constant is 3-normal. - Charles R Greathouse IV, Feb 06 2015

Examples

			0.598958167538433992500172217929...
		

Crossrefs

Cf. A054635 (base 3 digits), A077772 (continued fraction).
Cf. A030190, A066716, A066717: binary digits, decimals and continued fraction of the binary Champernowne constant; A033307: decimal Champernowne constant.

Programs

  • Mathematica
    First[RealDigits[ChampernowneNumber[3], 10, 100]] (* Paolo Xausa, May 03 2024 *)
  • PARI
    A077771(b=3,t=1.,s=b)={sum(n=1, default(realprecision)*2.303\log(b)+1, nM. F. Hasler, Oct 25 2019

A378328 Decimal expansion of the base 4 Champernowne constant.

Original entry on oeis.org

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

Views

Author

Joshua Searle, Nov 23 2024

Keywords

Comments

This constant is formed by the concatenation of the natural numbers in base 4 and then converted into base 10.
This constant is 4-normal.

Examples

			0.426111111111111065764556571420161985095546238967230410682791635172587553...
		

Crossrefs

Cf. A030302, A003137, A030373, A031219, A030548, A030998, A054634, A031076, A033307 (base n expansions of base n Champernowne constants, without leading zero, for 2 <= n <= 10).
Cf. A066716, A077771, A378328, A378329, A378330, A378331, A378332, A378333, A033307 (decimal expansions of base n Champernowne constants for 2 <= n <= 10).
Cf. A066717, A077772, A378345, A378346, A378347, A378348, A378349, A378350, A030167 (continued fraction expansions of base n Champernowne constants for 2 <= n <= 10).

Programs

  • Mathematica
    First[RealDigits[ChampernowneNumber[4], 10, 100]]

A378329 Decimal expansion of the base 5 Champernowne constant.

Original entry on oeis.org

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

Views

Author

Joshua Searle, Nov 23 2024

Keywords

Comments

This constant is formed by the concatenation of the natural numbers in base 5 and then converted into base 10.
This constant is 5-normal.

Examples

			0.310736111111111111111111111110963033311604944849115504682622268470343392...
		

Crossrefs

Cf. A030302, A003137, A030373, A031219, A030548, A030998, A054634, A031076, A033307 (base n expansions of base n Champernowne constants, without leading zero, for 2 <= n <= 10).
Cf. A066716, A077771, A378328, A378329, A378330, A378331, A378332, A378333, A033307 (decimal expansions of base n Champernowne constants for 2 <= n <= 10).
Cf. A066717, A077772, A378345, A378346, A378347, A378348, A378349, A378350, A030167 (continued fraction expansions of base n Champernowne constants for 2 <= n <= 10).

Programs

  • Mathematica
    First[RealDigits[ChampernowneNumber[5], 10, 100]]

A378330 Decimal expansion of the base 6 Champernowne constant.

Original entry on oeis.org

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

Views

Author

Joshua Searle, Nov 23 2024

Keywords

Comments

This constant is formed by the concatenation of the natural numbers in base 6 and then converted into base 10.
This constant is 6-normal.

Examples

			0.239862685815066767447719828672209624590576971529350213760693195631576583...
		

Crossrefs

Cf. A030302, A003137, A030373, A031219, A030548, A030998, A054634, A031076, A033307 (base n expansions of base n Champernowne constants, without leading zero, for 2 <= n <= 10).
Cf. A066716, A077771, A378328, A378329, A378330, A378331, A378332, A378333, A033307 (decimal expansions of base n Champernowne constants for 2 <= n <= 10).
Cf. A066717, A077772, A378345, A378346, A378347, A378348, A378349, A378350, A030167 (continued fraction expansions of base n Champernowne constants for 2 <= n <= 10).

Programs

  • Mathematica
    First[RealDigits[ChampernowneNumber[6], 10, 100]]
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