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 19 results. Next

A066096 a(n) = floor(n*phi), where phi = (1 + sqrt(5))/2.

Original entry on oeis.org

0, 1, 3, 4, 6, 8, 9, 11, 12, 14, 16, 17, 19, 21, 22, 24, 25, 27, 29, 30, 32, 33, 35, 37, 38, 40, 42, 43, 45, 46, 48, 50, 51, 53, 55, 56, 58, 59, 61, 63, 64, 66, 67, 69, 71, 72, 74, 76, 77, 79, 80, 82, 84, 85, 87, 88, 90, 92, 93, 95, 97, 98, 100, 101, 103, 105, 106
Offset: 0

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Author

Michele Dondi (bik.mido(AT)tiscalenet.it), Dec 30 2001

Keywords

Comments

a(n) is the smallest number different from a(i) and a(i)+i for i < n.
The losing positions in the game of Wythoff-Nim are precisely the pairs (a(n), a(n)+n).

Crossrefs

Programs

  • Magma
    [Floor((1+Sqrt(5))*n/2): n in [0..80]]; // G. C. Greubel, Sep 12 2023
    
  • Mathematica
    Floor[GoldenRatio*Range[0, 80]] (* G. C. Greubel, Sep 12 2023 *)
  • PARI
    a(n) = (n+sqrtint(5*n^2))\2;
    [a(n)|n<-[0..100]] \\ Simon Strandgaard, Jun 28 2022
    
  • SageMath
    [floor(golden_ratio*n) for n in range(81)] # G. C. Greubel, Sep 12 2023

Formula

For n >= 1, a(n) = A000201(n).
Duplicate values in A060143.
a(n) = 1 + A022342(n) = A000201(n).
a(n) = floor(n*phi), where phi = (1 + sqrt(5))/2. - Peter Munn, Jan 12 2018
a(n) = A026351(n) - 1. - Philippe Deléham, Jan 15 2023

Extensions

Name corrected by Peter Munn, Dec 06 2017
New name using a formula from Peter Munn by Peter Luschny, Jan 18 2023

A004922 a(n) = floor(n*phi^7), where phi is the golden ratio, A001622.

Original entry on oeis.org

0, 29, 58, 87, 116, 145, 174, 203, 232, 261, 290, 319, 348, 377, 406, 435, 464, 493, 522, 551, 580, 609, 638, 667, 696, 725, 754, 783, 812, 841, 871, 900, 929, 958, 987, 1016, 1045, 1074, 1103, 1132, 1161, 1190, 1219, 1248, 1277, 1306, 1335, 1364
Offset: 0

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Author

Keywords

Crossrefs

Programs

  • Magma
    [Floor(n*((1 + Sqrt(5))/2)^7): n in [0..50]]; // Vincenzo Librandi, Jul 22 2015
  • Mathematica
    Table[Floor[n ((1 + Sqrt[5])/2)^7], {n, 0, 50}] (* Vincenzo Librandi, Jul 22 2015 *)
  • Python
    from sympy import sqrt
    phi = (1 + sqrt(5))/2
    for n in range(0,101): print(int(n*phi**7), end=', ') # Karl V. Keller, Jr., Jul 22 2015
    

A090909 Terms a(k) of A073869 for which a(k-1) = a(k), and a(k) and a(k+1) are distinct.

Original entry on oeis.org

2, 5, 7, 10, 13, 15, 18, 20, 23, 26, 28, 31, 34, 36, 39, 41, 44, 47, 49, 52, 54, 57, 60, 62, 65, 68, 70, 73, 75, 78, 81, 83, 86, 89, 91, 94, 96, 99, 102, 104, 107, 109, 112, 115, 117, 120, 123, 125, 128, 130, 133, 136, 138, 141, 143, 146, 149, 151, 154, 157, 159, 162
Offset: 1

Views

Author

Amarnath Murthy, Dec 14 2003

Keywords

Comments

Is this the same as A001950? - Alec Mihailovs (alec(AT)mihailovs.com), Jul 23 2007
Identical to n + A066096(n)? - Ed Russell (times145(AT)hotmail.com), May 09 2009
From Michel Dekking, Dec 18 2024: (Start)
Proof of Mihailovs's conjecture: This follows immediately from the result in my 2023 paper in JIS that A073869 is equal to Hofstadter’s G-sequence A005206, and my recent comment in A005206 on the pairs of duplicate values in A005206.
The answer to Russell’s question is well-known, and also Detlef’s formula is well-known.
Originally, this sequence was given the name “Terms a(k) of A073869 for which a(k-1), a(k) and a(k+1) are distinct.’’ These are the triples (1,2,3),(4,5,6),(6,7,8), (9,10,11), ... occurring at k = 3, k = 8, k = 11, k = 16,... in A005206. Note that if a duplicate pair (a(m-1), a(m)) is followed directly by another duplicate pair, then a(m-3), a(m-2) and a(m-1) are distinct, and only so. This corresponds to the block 00 occurring in the Fibonacci word obtained by projecting A005206 on the Fibonacci word (see Corollary in my recent comment in A005206). These occurrences are at the Wythoff AB numbers A003623 according to Wolfdieter Lang’s comment in A003623. Conclusion: the sequence of terms a(k) of A073869 for which a(k-1), a(k), and a(k+1) are distinct is given by the Wythoff AB-numbers. (End)

Examples

			A073869 = A005206 = 0,1,1,2,3,3,4,4,5,6,6,... The pair (1,1) occurs at k = 2.
		

Crossrefs

Programs

  • Magma
    [Floor((3+Sqrt(5))*n/2): n in [0..80]]; // G. C. Greubel, Sep 12 2023
    
  • Mathematica
    (* First program *)
    A002251= Fold[Append[#1, #2 Ceiling[#2/GoldenRatio] -Total[#1]] &, {1}, Range[2, 500]] - 1; (* Birkas Gyorgy's code of A019444, modified *)
    A090909= Join[{0}, Select[Partition[A002251, 2, 1], #[[2]] > #[[1]] &][[All, 2]]] (* G. C. Greubel, Sep 12 2023 *)
    (* Second program *)
    Floor[GoldenRatio^2*Range[0,80]] (* G. C. Greubel, Sep 12 2023 *)
  • SageMath
    [floor(golden_ratio^2*n) for n in range(81)] # G. C. Greubel, Sep 12 2023

Formula

a(n) = floor(phi^2*n), where phi = (1+sqrt(5))/2. - Gary Detlefs, Mar 10 2011

Extensions

More terms from R. J. Mathar, Sep 29 2017
Name corrected by Michel Dekking, Dec 13 2024

A004919 a(n) = floor(n*phi^4), where phi is the golden ratio, A001622.

Original entry on oeis.org

0, 6, 13, 20, 27, 34, 41, 47, 54, 61, 68, 75, 82, 89, 95, 102, 109, 116, 123, 130, 137, 143, 150, 157, 164, 171, 178, 185, 191, 198, 205, 212, 219, 226, 233, 239, 246, 253, 260, 267, 274, 281, 287, 294, 301, 308
Offset: 0

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Author

Keywords

Comments

The golden section or golden ratio is now usually denoted by "phi", but it in the older literature it was more often denoted by "tau." - N. J. A. Sloane, Feb 17 2013

Crossrefs

Programs

  • Magma
    [Floor((7+3*Sqrt(5))*n/2): n in [0..60]]; // G. C. Greubel, Aug 22 2023
    
  • Mathematica
    With[{c=GoldenRatio^4},Floor[c*Range[0,50]]] (* Harvey P. Dale, Apr 11 2012 *)
  • Python
    from math import isqrt
    def A004919(n): return (3*n+isqrt(45*n**2)>>1)+(n<<1) # Chai Wah Wu, Aug 17 2022
    
  • SageMath
    [floor(golden_ratio^4*n) for n in range(61)] # G. C. Greubel, Aug 22 2023

Formula

a(n) = 2*n + floor(3*n*tau). [Formula corrected by Charles R Greathouse IV, Mar 11 2011]

A004924 a(n) = floor(n*phi^9), where phi is the golden ratio, A001622.

Original entry on oeis.org

0, 76, 152, 228, 304, 380, 456, 532, 608, 684, 760, 836, 912, 988, 1064, 1140, 1216, 1292, 1368, 1444, 1520, 1596, 1672, 1748, 1824, 1900, 1976, 2052, 2128, 2204, 2280, 2356, 2432, 2508, 2584, 2660, 2736
Offset: 0

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Keywords

Comments

The first differences a(n) - a(n-1) generally equal 76 with exceptions for example at n = 77, 153, 229, 305, 381, 457, ..., 5777, 5854, 5930, .... where they equal 77. - R. J. Mathar, Jan 11 2008

Crossrefs

Programs

  • Magma
    [Floor((38+17*Sqrt(5))*n): n in [0..60]]; // G. C. Greubel, Aug 24 2023
    
  • Mathematica
    Floor[GoldenRatio^9*Range[0, 60]] (* G. C. Greubel, Aug 24 2023 *)
  • SageMath
    [floor(golden_ratio^9*n) for n in range(61)] # G. C. Greubel, Aug 24 2023

A004926 a(n) = floor(n*phi^11), where phi is the golden ratio, A001622.

Original entry on oeis.org

0, 199, 398, 597, 796, 995, 1194, 1393, 1592, 1791, 1990, 2189, 2388, 2587, 2786, 2985, 3184, 3383, 3582, 3781, 3980, 4179, 4378, 4577, 4776, 4975, 5174, 5373, 5572, 5771, 5970, 6169, 6368, 6567, 6766
Offset: 0

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Author

Keywords

Crossrefs

Programs

  • Magma
    [Floor((199+89*Sqrt(5))*n/2): n in [0..60]]; // G. C. Greubel, Aug 27 2023
    
  • Mathematica
    Floor[GoldenRatio^(11)*Range[0, 60]] (* G. C. Greubel, Aug 27 2023 *)
  • SageMath
    [floor(golden_ratio^(11)*n) for n in range(61)] # G. C. Greubel, Aug 27 2023

A004928 a(n) = floor(n*phi^13), where phi is the golden ratio, A001622.

Original entry on oeis.org

0, 521, 1042, 1563, 2084, 2605, 3126, 3647, 4168, 4689, 5210, 5731, 6252, 6773, 7294, 7815, 8336, 8857, 9378, 9899, 10420, 10941, 11462, 11983, 12504, 13025, 13546, 14067, 14588, 15109, 15630, 16151
Offset: 0

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Author

Keywords

Crossrefs

Programs

  • Magma
    [Floor((521+233*Sqrt(5))*n/2): n in [0..60]]; // G. C. Greubel, Sep 05 2023
    
  • Mathematica
    Floor[GoldenRatio^(13)*Range[0, 60]] (* G. C. Greubel, Sep 05 2023 *)
  • SageMath
    [floor(golden_ratio^(13)*n) for n in range(61)] # G. C. Greubel, Sep 05 2023

A004930 a(n) = floor(n*phi^15), where phi is the golden ratio, A001622.

Original entry on oeis.org

0, 1364, 2728, 4092, 5456, 6820, 8184, 9548, 10912, 12276, 13640, 15004, 16368, 17732, 19096, 20460, 21824, 23188, 24552, 25916, 27280, 28644, 30008, 31372, 32736, 34100, 35464, 36828, 38192
Offset: 0

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Author

Keywords

Crossrefs

Programs

  • Magma
    [Floor((682+305*Sqrt(5))*n): n in [0..60]]; // G. C. Greubel, Sep 05 2023
    
  • Mathematica
    Floor[GoldenRatio^(15)*Range[0, 60]] (* G. C. Greubel, Sep 05 2023 *)
  • SageMath
    [floor(golden_ratio^(15)*n) for n in range(61)] # G. C. Greubel, Sep 05 2023

A004934 a(n) = floor(n*phi^19), where phi is the golden ratio, A001622.

Original entry on oeis.org

0, 9349, 18698, 28047, 37396, 46745, 56094, 65443, 74792, 84141, 93490, 102839, 112188, 121537, 130886, 140235, 149584, 158933, 168282, 177631, 186980, 196329, 205678, 215027, 224376, 233725
Offset: 0

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Author

Keywords

Crossrefs

Programs

  • Magma
    [Floor((9349+4181*Sqrt(5))*n/2): n in [0..60]]; // G. C. Greubel, Sep 12 2023
    
  • Mathematica
    Floor[GoldenRatio^(19)*Range[0, 60]] (* G. C. Greubel, Sep 12 2023 *)
  • SageMath
    [floor(golden_ratio^(19)*n) for n in range(61)] # G. C. Greubel, Sep 12 2023

A004920 a(n) = floor(n*phi^5), where phi is the golden ratio, A001622.

Original entry on oeis.org

0, 11, 22, 33, 44, 55, 66, 77, 88, 99, 110, 121, 133, 144, 155, 166, 177, 188, 199, 210, 221, 232, 243, 255, 266, 277, 288, 299, 310, 321, 332, 343, 354, 365, 377, 388, 399, 410, 421, 432, 443, 454, 465, 476, 487, 499, 510, 521, 532, 543, 554, 565, 576, 587, 598
Offset: 0

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Author

Keywords

Crossrefs

Programs

  • Magma
    [Floor((11+5*Sqrt(5))*n/2): n in [0..60]]; // G. C. Greubel, Aug 22 2023
    
  • Mathematica
    Table[Floor[n GoldenRatio^5],{n,0,54}] (* Stefano Spezia, Feb 19 2023 *)
  • SageMath
    [floor(golden_ratio^5*n) for n in range(61)] # G. C. Greubel, Aug 22 2023
Showing 1-10 of 19 results. Next