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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A110294 a(2*n) = A028230(n), a(2*n+1) = -A067900(n+1).

Original entry on oeis.org

1, -8, 15, -112, 209, -1560, 2911, -21728, 40545, -302632, 564719, -4215120, 7865521, -58709048, 109552575, -817711552, 1525870529, -11389252680, 21252634831, -158631825968, 296011017105, -2209456310872, 4122901604639, -30773756526240, 57424611447841
Offset: 0

Views

Author

Creighton Dement, Jul 18 2005

Keywords

Comments

See A110293.

Crossrefs

Programs

  • Magma
    [(3*(-1)^n-1)*Evaluate(ChebyshevSecond(n+1), 2)/2: n in [0..40]]; // G. C. Greubel, Jan 04 2023
    
  • Maple
    seriestolist(series((1-8*x+x^2)/((x^2-4*x+1)*(x^2+4*x+1)), x=0,25));
  • Mathematica
    CoefficientList[Series[(1-8x+x^2)/((1-4x+x^2)(1+4x+x^2)), {x, 0, 24}], x] (* Michael De Vlieger, Nov 01 2016 *)
    LinearRecurrence[{0,14,0,-1},{1,-8,15,-112},30] (* Harvey P. Dale, Dec 16 2024 *)
  • PARI
    Vec((1-8*x+x^2)/((1-4*x+x^2)*(1+4*x+x^2)) + O(x^30)) \\ Colin Barker, Nov 01 2016
    
  • SageMath
    [(3*(-1)^n-1)*chebyshev_U(n,2)/2 for n in range(41)] # G. C. Greubel, Jan 04 2023

Formula

G.f.: (1-8*x+x^2) / ((1-4*x+x^2)*(1+4*x+x^2)).
a(n) = 14*a(n-2) - a(n-4) for n>3. - Colin Barker, Nov 01 2016
a(n) = (3*(-1)^n - 1)*A001353(n+1)/2. - R. J. Mathar, Sep 11 2019

A232765 Values of y solving x^2 = floor(y^2/3 + y).

Original entry on oeis.org

0, 1, 4, 9, 28, 73, 144, 409, 1036, 2025, 5716, 14449, 28224, 79633, 201268, 393129, 1109164, 2803321, 5475600, 15448681, 39045244, 76265289, 215172388, 543830113, 1062238464, 2996964769, 7574576356, 14795073225, 41742334396, 105500238889, 206068786704, 581395716793, 1469428768108
Offset: 1

Views

Author

Richard R. Forberg, Nov 29 2013

Keywords

Comments

The corresponding values of x are given by A232771.
a(n) + 3 gives the values of y solving x^2 = floor(y^2/3 - y), and yields the same values for x.
a(3n+1) are squares whose square roots are given by A005320.
Let b(n) equal the second differences of a(n) where b(1) = 2. Then, for n>0, b(3n-1) = b(3n-2) = 2* A001570(n+1); b(3n)= 2*A011943(n); and b(3n) = (b(3n+1) + b(3n-1))/2.

Crossrefs

Programs

  • PARI
    is(n)=issquare(n^2\3+n)
    print1("0, 1");for(x=3,99,y=round(sqrt(3)*x-3/2);if(is(y),print1(", "y))) \\ Charles R Greathouse IV, Dec 09 2013

Formula

Empirical g.f.: -x^2*(x+1)*(x^2+x+1)^2 / ((x-1)*(x^6-14*x^3+1)). - Colin Barker, Dec 30 2014

Extensions

a(23) corrected by Colin Barker, Dec 30 2014
Showing 1-2 of 2 results.