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 84 results. Next

A124841 Inverse binomial transform of A005614, the rabbit sequence: (1, 0, 1, 1, 0, ...).

Original entry on oeis.org

1, -1, 2, -3, 3, 0, -10, 35, -90, 200, -400, 726, -1188, 1716, -2080, 1820, -312, -2704, 5408, 455, -39195, 170313, -523029, 1352078, -3114774, 6548074, -12668578, 22492886, -36020998, 49549110, -49549110, 0, 182029056, -670853984, 1809734560, -4242470755
Offset: 0

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Author

Gary W. Adamson, Nov 10 2006

Keywords

Comments

As with every inverse binomial transform, the numbers are given by starting from the sequence (A005614) and reading the leftmost values of the array of repeated differences.

Examples

			Given 1, 0, 1, 1, 0, ..., take finite difference rows:
1, 0, 1, 1, 0, ...
_-1, 1, 0, -1, ...
___ 2, -1, -1, ...
_____ -3, 0, ...
________ 3, ...
Left border becomes the sequence.
		

Crossrefs

Cf. A124842.
The following sequences are all essentially the same, in the sense that they are simple transformations of each other, with A000201 as the parent: A000201, A001030, A001468, A001950, A003622, A003842, A003849, A004641, A005614, A014675, A022342, A088462, A096270, A114986, A124841. - N. J. A. Sloane, Mar 11 2021

Programs

  • Mathematica
    A005614 = SubstitutionSystem[{0 -> {1}, 1 -> {1, 0}}, {1, 0}, 7] // Last;
    Table[Differences[A005614, n], {n, 0, 35}][[All, 1]] (* Jean-François Alcover, Feb 06 2020 *)

Extensions

Corrected and extended by R. J. Mathar, Nov 28 2011

A089910 Indices n at which blocks (1;1) occur in infinite Fibonacci word, i.e., such that A005614(n-1) = A005614(n-2) = 1.

Original entry on oeis.org

4, 9, 12, 17, 22, 25, 30, 33, 38, 43, 46, 51, 56, 59, 64, 67, 72, 77, 80, 85, 88, 93, 98, 101, 106, 111, 114, 119, 122, 127, 132, 135, 140, 145, 148, 153, 156, 161, 166, 169, 174, 177, 182, 187, 190, 195, 200, 203, 208, 211, 216, 221, 224, 229, 232, 237, 242, 245
Offset: 1

Views

Author

Benoit Cloitre, Nov 15 2003

Keywords

Comments

a(n) is the number k such that floor(k/r) = floor(n*r^2), where r = golden ratio. - Clark Kimberling, May 03 2015

Crossrefs

Programs

  • Maple
    phi:=(1+sqrt(5))/2:  seq(floor(phi*floor(n*phi^2))+1, n=1..80); # Michel Dekking, Sep 15 2016
  • Mathematica
    r = GoldenRatio; u = Flatten[Table[Select[Range[Floor[(r^2 + r) n], Floor[(r^2 + r) n + 1]], Floor[#/r] == Floor[n*r^2] &], {n, 1, 100}]] (* Clark Kimberling, May 03 2015 *)
  • Python
    from math import isqrt
    def A089910(n): return (n+isqrt(5*n**2)&-2)+n+1 # Chai Wah Wu, Aug 29 2022

Formula

a(n) = floor((2+sqrt(5))*n) + 0 or 1;
floor(n*(2+sqrt(5))) + b(a(n)) - a(n) = 0 where b(x) = A078588(x) = x + 1 + ceiling(x*sqrt(5)) - 2*ceiling(x*(1+sqrt(5))/2).
For n >= 2, a(n) = a(n-1) + d, where d = 5 if n-1 is in A000201, else d = 3. - Clark Kimberling, May 03 2015
a(n) = A003623(n) + 1 = A(B(n)) + 1, where A(B(n)) are the Wythoff AB-numbers. - Michel Dekking, Sep 15 2016

Extensions

Definition corrected by Jeffrey Shallit, Dec 21 2023

A044432 a(n) is the number whose base-2 representation is d(0)d(1)...d(n), where d=A005614 (the infinite Fibonacci word).

Original entry on oeis.org

1, 2, 5, 11, 22, 45, 90, 181, 363, 726, 1453, 2907, 5814, 11629, 23258, 46517, 93035, 186070, 372141, 744282, 1488565, 2977131, 5954262, 11908525, 23817051, 47634102, 95268205, 190536410, 381072821, 762145643, 1524291286, 3048582573, 6097165147, 12194330294
Offset: 0

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Author

Keywords

Comments

a(n) can also be calculated as floor(2^n * R), where the rabbit constant R=0.709803442861291314641787399444575597012... converges rapidly using the result from Davison described in the comments at A014565. - Federico Provvedi, Oct 24 2018

Crossrefs

Programs

  • Haskell
    a044432 n = a044432_list !! n
    a044432_list = scanl1 (\v b -> 2 * v + b) a005614_list
    -- Reinhard Zumkeller, Apr 07 2012
  • Mathematica
    FromDigits[(Floor[GoldenRatio(#+1)]-Floor[GoldenRatio #]-1)&@Range@#,2]&/@Range@40 (* Federico Provvedi, Oct 19 2018 *)
    Floor[2^#/FromContinuedFraction[2^Fibonacci[Range[0,3*Max[1,Floor[2+Log[(#+1)/11]/ArcSinh[2]]]]]]]&/@Range[200] (* Federico Provvedi, Nov 01 2018 *)

Formula

a(n) = A000225(n+1) - A182028(n). - Reinhard Zumkeller, Apr 07 2012
a(n) = 2*a(n-1) + A005614(n) for n > 0, a(0) = 1. - Reinhard Zumkeller, Apr 07 2012
From Federico Provvedi, Oct 24 2018: (Start)
a(n) = A000079(n) * Sum_{k=0..n} ((floor(phi*(k+1)) - floor(phi*k) - 1)/2^k).
a(n) = floor(2^n*(1-Sum_{n >= 1} (-1)^(n+1)*(1+2^Fibonacci(3*n+1))/((2^(Fibonacci(3*n-1))-1)*(2^(Fibonacci(3*n + 2))-1)))).
a(n) = floor(2^n*R), where R is the rabbit constant.
a(n) = floor(2^n/[1, 2, 2, 4, 8, 32, ..., 2^Fibonacci(3*h)]), with h=1 for n=0, h=floor(2+log((n+1)/11)/arcsinh(2)) for n>0. (End)

Extensions

Offset fixed by Reinhard Zumkeller, Apr 07 2012

A178992 Ordered list in decimal notation of the subwords (with leading zeros omitted) appearing in the infinite Fibonacci word A005614 (0->1 & 1->10).

Original entry on oeis.org

0, 1, 2, 3, 5, 6, 10, 11, 13, 21, 22, 26, 27, 43, 45, 53, 54, 86, 90, 91, 107, 109, 173, 181, 182, 214, 218, 346, 347, 363, 365, 429, 437, 693, 694, 726, 730, 858, 859, 875, 1387, 1389, 1453, 1461, 1717, 1718, 1750, 2774, 2778, 2906, 2907, 2923, 3435, 3437, 3501
Offset: 1

Views

Author

Alexandre Losev, Jan 03 2011

Keywords

Comments

The definition mentions the Fibonacci word A005614. Note that the official Fibonacci word is A003849, which would give a different list, namely, the 2's-complement of the present list. - N. J. A. Sloane, Jan 12 2011

Examples

			The Fibonacci word has a minimal complexity, i.e., for any n there are n+1 distinct subwords of length n (see for example Allouche and Shallit).
E.g. for n=1 they are '0' and '1', for n=2 '01', '10' and '11' or, in decimal notation '1','2',and '3'.
Some subwords prefixed with '0' have the same decimal value as shorter ones, but there is no real ambiguity as double zeros do not appear in the infinite Fibonacci word.
		

References

  • J.-P. Allouche and J. Shallit, Automatic Sequences, Cambridge Univ. Press, 2003.

Crossrefs

Programs

  • Mathematica
    iter=8; f=Nest[Flatten[# /. {0 -> {1}, 1 -> {1, 0}}] &, {1}, iter]; u={}; n=1; While[lst={}; k=0; While[num=FromDigits[Take[f, {1, n}+k], 2]; lst=Union[lst, {num}]; Length[lst]
    				

Extensions

Definition clarified by N. J. A. Sloane, Jan 10 2011

A028894 a(n) = either 4a(n-1)+1 or 4a(n-1)+3 depending on corresponding term of A005614, +1 for 0, +3 for 1.

Original entry on oeis.org

1, 5, 23, 95, 381, 1527, 6109, 24439, 97759, 391037, 1564151, 6256607, 25026429, 100105719, 400422877, 1601691511, 6406766047, 25627064189, 102508256759, 410033027037, 1640132108151, 6560528432607, 26242113730429
Offset: 1

Views

Author

John McNamara, Jan 12 2002

Keywords

Crossrefs

Programs

  • Mathematica
    f[1]={0}; f[2]={1}; f[n_] := f[n]=Join[f[n-1], f[n-2]]; a[1]=1; a[n_] := a[n]=4a[n-1]+1+2f[9][[n]]; a/@Range[1, 30]

Extensions

Edited by Dean Hickerson, Jan 14 2002

A179969 Ordered list in decimal notation of the subwords appearing in the infinite Fibonacci word A005614.

Original entry on oeis.org

0, 1, 1, 2, 3, 2, 3, 5, 6, 5, 6, 10, 11, 13, 11, 13, 21, 22, 26, 27, 22, 26, 27, 43, 45, 53, 54, 45, 53, 54, 86, 90, 91, 107, 109, 90, 91, 107, 109, 173, 181, 182, 214, 218, 181, 182, 214, 218, 346, 347, 363, 365, 429, 437, 363, 365, 429, 437, 693, 694, 726, 730, 858, 859, 875, 726, 730, 858, 859, 875
Offset: 1

Views

Author

T. D. Noe, Jan 12 2011

Keywords

Comments

See A178992 for more details. In binary, the subwords are 0, 1, 01, 10, 11, 010, 011, 101, 110, 0101, 0110, 1010, 1011, 1101,... Converting these numbers to decimal produces this sequence. Except for the initial 0, subwords of the form 0X occur later in the sequence than X. Hence, the second occurrence of a number in this sequence represents the subword having a leading zero. There is a link to a file containing the subwords in binary.

Programs

  • Mathematica
    iter=8; f=Nest[Flatten[#/.{0->{1},1->{1,0}}]&,{1},iter]; u={}; n=1; While[lst={}; k=0; While[num=FromDigits[Take[f,{1,n}+k],2]; lst=Union[lst,{num}]; Length[lst]
    				

A066744 a(n) = either 4a(n-1)+1 or 4a(n-1)+3 depending on corresponding term of A005614, +3 for 0, +1 for 1.

Original entry on oeis.org

1, 7, 29, 117, 471, 1885, 7543, 30173, 120693, 482775, 1931101, 7724405, 30897623, 123590493, 494361975, 1977447901, 7909791605, 31639166423, 126556665693, 506226662775, 2024906651101, 8099626604405, 32398506417623
Offset: 1

Views

Author

John McNamara, Jan 16 2002

Keywords

Comments

Ratio to terms of A028894 tends to 1.23459972586...

Crossrefs

Programs

  • Mathematica
    f[1]={0}; f[2]={1}; f[n_] := f[n]=Join[f[n-1], f[n-2]]; a[1]=1; a[n_] := a[n]=4a[n-1]+3-2f[9][[n]]; a/@Range[1, 30]

A124842 Triangle, row sums = A005614, the rabbit sequence.

Original entry on oeis.org

1, 1, -1, 1, -2, 2, 1, -3, 6, -3, 1, -4, 12, -12, 3, 1, -5, 20, -30, 15, 0, 1, -6, 30, -60, 45, 0, -10, 1, -7, 42, -105, 105, 0, -70, 35, 1, -8, 56, -168, 210, 0, -280, 280, -90
Offset: 1

Views

Author

Gary W. Adamson, Nov 10 2006

Keywords

Examples

			First few rows of the triangle are:
1;
1, -1;
1, -2, 2;
1, -3, 6, -3;
1, -4, 12, -12, 3;
1, -5, 20, -30, 15, 0;
1, -6, 30, -60, 45, 0, -10;
...
4th term of the rabbit sequence (1, 0, 1, 1, 0...) = 1 = sum of row 4 terms: (1, - 3 + 6 - 3).
		

Crossrefs

Cf. A124841.

Formula

Binomial transform of the infinite matrix with the diagonalized sequence A124841.

A144023 INVERT transform of the rabbit sequence, A005614.

Original entry on oeis.org

1, 1, 2, 4, 6, 10, 17, 29, 49, 82, 138, 234, 394, 663, 1118, 1886, 3179, 5358, 9032, 15227, 25670, 43272, 72945, 122970, 207300, 349456, 589098, 993082, 1674103, 2822138, 4757452, 8019937, 13519716, 22791031, 38420264, 64767451
Offset: 1

Views

Author

Gary W. Adamson, Sep 07 2008

Keywords

Comments

a(n)/a(n-1) appears to converge to phi.
The sequence generated is first (1, 1, 1, 2, 4, 6, 10,...), but by convention we drop the first "1".
Equals row sums of triangle A144024.

Examples

			The operations in steps generate(1, 1, 1, 2...).
a(4) = 4 = (1, 1, 0, 1) dot (1, 1, 1, 2) = (1 + 1 + 0 + 2).
		

Crossrefs

A144024 Eigentriangle by rows, T(n,k) = A005614(n-k+1)*A144023(k-1).

Original entry on oeis.org

1, 0, 1, 1, 0, 1, 1, 1, 0, 2, 0, 1, 1, 0, 4, 1, 0, 1, 2, 0, 6, 0, 1, 0, 2, 4, 0, 10, 1, 0, 1, 0, 4, 6, 0, 17, 1, 1, 0, 20, 6, 10, 0, 29, 0, 1, 1, 0, 4, 0, 10, 17, 0, 4, 9, 1, 0, 1, 2, 0, 6, 0, 17, 29, 0, 82
Offset: 1

Views

Author

Gary W. Adamson, Sep 07 2008

Keywords

Comments

Row sums = A144023, the INVERT transform of the rabbit sequence, A005614.
Left border = A005614.
Sum of n-th row terms = rightmost term of next row.

Examples

			First few rows of the triangle =
  1;
  0, 1;
  1, 0, 1;
  1, 1, 0, 2;
  0, 1, 1, 0, 4;
  1, 0, 1, 2, 0, 6;
  0, 1, 0, 2, 4, 0, 10;
  1, 0, 1, 0, 4, 6, 0, 17;
  1, 1, 0, 2, 0, 6, 10, 0, 29;
  ...;
Row 4 = (1, 1, 0, 2) = termwise product of (1, 1, 0, 1) and (1, 1, 1, 2); where (1, 1, 0, 1) = the first 4 terms of A005614 reversed. (1, 1, 1, 2) = the first 4 terms of shifted A144023.
		

Crossrefs

Formula

Eigentriangle by rows, T(n,k) = A005614(n-k+1)*A144023(k-1).
A005614 = the rabbit sequence, (1, 0, 1, 1, 0, 1, 0, 1,...)
A144023(k-1) = A144023 shifted to (1, 1, 1, 2, 4, 6, 10, 17, 29,...).
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