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.

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A004696 a(n) = floor(Fibonacci(n)/3).

Original entry on oeis.org

0, 0, 0, 0, 1, 1, 2, 4, 7, 11, 18, 29, 48, 77, 125, 203, 329, 532, 861, 1393, 2255, 3648, 5903, 9552, 15456, 25008, 40464, 65472, 105937, 171409, 277346, 448756, 726103, 1174859, 1900962, 3075821, 4976784, 8052605, 13029389, 21081995, 34111385, 55193380
Offset: 0

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Keywords

Examples

			G.f. = x^4 + x^5 + 2*x^6 + 4*x^7 + 7*x^8 + 11*x^9 + 18*x^10 + 29*x^11 + 48*x^12 + ...
		

Crossrefs

Cf. A000045 (Fibonacci(n)).
Cf. A082115 (Fibonacci(n) (mod 3)).
Cf. A293543 (ceiling(Fibonacci(n)/3)).
Cf. A293544 (round(Fibonacci(n)/3)).

Programs

  • Magma
    [Floor(Fibonacci(n)/3): n in [0..40]]; // Vincenzo Librandi, Jul 09 2012
    
  • Maple
    seq(iquo(fibonacci(n),3),n=0..40); # Zerinvary Lajos, Apr 20 2008
  • Mathematica
    CoefficientList[Series[x^4 (x^4 + x^3 + 1)/((1 - x^8) (1 -x - x^2)), {x, 0, 40}], x] (* Vincenzo Librandi, Jul 09 2012 *)
    Floor[Fibonacci[Range[0, 40]]/3] (* G. C. Greubel, May 22 2019 *)
    Table[Floor[Fibonacci[n]/3], {n, 0, 20}] (* Eric W. Weisstein, Feb 09 2025 *)
    Table[(8 Fibonacci[n] + 3 (-1)^n - 9 + Cos[Pi n/2] (6 - 4 Sin[Pi n/4]) + 4 Sqrt[2] Sin[Pi n/4] Sin[Pi n/2])/24, {n, 0, 20}] (* Eric W. Weisstein, Feb 09 2025 *)
  • PARI
    vector(40, n, n--; fibonacci(n)\3) \\ Altug Alkan, Nov 06 2015
    
  • PARI
    concat(vector(4), Vec(x^4*(x^4+x^3+1)/((1-x^8)*(1-x-x^2)) + O(x^40))) \\ Altug Alkan, Nov 06 2015
    
  • Sage
    [floor(fibonacci(n)/3) for n in (0..40)] # G. C. Greubel, May 22 2019

Formula

G.f.: x^4*(1 +x^3 +x^4) / ((1-x^8)*(1-x-x^2)).
a(n) = (A000045(n) - A082115(n))/3. - R. J. Mathar, Jul 14 2012
From Vladimir Reshetnikov, Nov 05 2015: (Start)
a(n) = (8*A000045(n) + 3*(-1)^n - 9 + cos(Pi*n/2)*(6 - 4*sin(Pi*n/4)) + 4*sqrt(2)*sin(Pi*n/4)*sin(Pi*n/2))/24.
E.g.f.: (cos(x)-cosh(x)-2*sinh(x))/4 + (sqrt(2)*cos(x/sqrt(2))+sin(x/sqrt(2)))*sinh(x/sqrt(2))/6 + 2*exp(x/2)*sinh(x*sqrt(5)/2)/(3*sqrt(5)). (End)
The sequence b(n) = a(n+2) - a(n+1) - a(n) has period 8 and always 0 or 1. - Michael Somos, Nov 06 2015

A293544 a(n) = round(Fibonacci(n)/3).

Original entry on oeis.org

0, 0, 0, 1, 1, 2, 3, 4, 7, 11, 18, 30, 48, 78, 126, 203, 329, 532, 861, 1394, 2255, 3649, 5904, 9552, 15456, 25008, 40464, 65473, 105937, 171410, 277347, 448756, 726103, 1174859, 1900962, 3075822, 4976784, 8052606, 13029390, 21081995, 34111385, 55193380
Offset: 0

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Author

Clark Kimberling, Oct 12 2017

Keywords

Comments

a(n) is the integer k that minimizes | k/Fibonacci(n) - 1/3 |.

Crossrefs

Cf. A000045 (Fibonacci(n)).
Cf. A004696 (floor(Fibonacci(n)/3)).
Cf. A293543 (ceiling(Fibonacci(n)/3)).

Programs

  • Mathematica
    Table[Round[Fibonacci[n]/3], {n, 0, 20}] (* Eric W. Weisstein, Feb 08 2025 *)
    Round[Fibonacci[Range[0, 20]]/3] (* Eric W. Weisstein, Feb 08 2025 *)
    LinearRecurrence[{1, 1, 0, -1, 1, 1}, {0, 0, 1, 1, 2, 3}, {0, 20}] (* Eric W. Weisstein, Feb 08 2025 *)
    CoefficientList[Series[-(x^3/((-1 + x + x^2) (1 + x^4))), {x, 0, 20}], x] (* Eric W. Weisstein, Feb 08 2025 *)
    Table[(Fibonacci[n] + (-1)^n Sin[n Pi/4] (Cos[n Pi/2] + Sqrt[2] Sin[n Pi/2]))/3, {n, 0, 20}] (* Eric W. Weisstein, Feb 08 2025 *)

Formula

G.f.: -(x^2/((-1 + x + x^2) (1 + x^4))).
a(n) = a(n-1) + a(n-2) - a(n-4) + a(n-5) + a(n-6) for n >= 7.
Showing 1-2 of 2 results.