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.

A093131 Binomial transform of Fibonacci(2n).

Original entry on oeis.org

0, 1, 5, 20, 75, 275, 1000, 3625, 13125, 47500, 171875, 621875, 2250000, 8140625, 29453125, 106562500, 385546875, 1394921875, 5046875000, 18259765625, 66064453125, 239023437500, 864794921875, 3128857421875, 11320312500000, 40957275390625, 148184814453125
Offset: 0

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Author

Paul Barry, Mar 23 2004

Keywords

Comments

Second binomial transform of Fibonacci(n). - Paul Barry, Apr 22 2005

Crossrefs

Programs

  • GAP
    a:=[0,1];; for n in [3..30] do a[n]:=5*(a[n-1]-a[n-2]); od; a; # G. C. Greubel, Dec 27 2019
  • Magma
    I:=[0,1]; [n le 2 select I[n] else 5*(Self(n-1) - Self(n-2)): n in [1..30]]; // G. C. Greubel, Dec 27 2019
    
  • Maple
    seq(coeff(series(x/(1-5*x+5*x^2), x, n+1), x, n), n = 0..30); # G. C. Greubel, Dec 27 2019
  • Mathematica
    CoefficientList[Series[x/(1-5x+5x^2), {x,0,30}], x] (* Michael De Vlieger, Dec 22 2019 *)
    Table[If[EvenQ[n], 5^(n/2)*Fibonacci[n], 5^((n-1)/2)*LucasL[n]], {n,0,30}] (* G. C. Greubel, Dec 27 2019 *)
    LinearRecurrence[{5,-5},{0,1},30] (* Harvey P. Dale, Mar 21 2023 *)
  • PARI
    my(x='x+O('x^30)); concat([0], Vec(x/(1-5*x+5*x^2))) \\ G. C. Greubel, Dec 27 2019
    
  • Sage
    def A093131_list(prec):
        P. = PowerSeriesRing(ZZ, prec)
        return P( x/(1-5*x+5*x^2) ).list()
    A093131_list(30) # G. C. Greubel, Dec 27 2019
    

Formula

G.f.: x/(1 - 5*x + 5*x^2).
a(n) = 5*a(n-1) - 5*a(n-2).
a(n) = (((5 + sqrt(5))/2)^n - ((5 - sqrt(5))/2)^n)/sqrt(5).
a(n) = A093130(n)/2^n.
a(n) = Sum_{k=0..n} Sum_{j=0..n} C(n, j)*C(j, k)*Fibonacci(j-k). - Paul Barry, Feb 15 2005
a(n) = Sum_{k=0..n} C(n, k)*2^k*Fibonacci(n-k) = Sum_{k=0..n} C(n, k)*2^(n-k) * Fibonacci(k). - Paul Barry, Apr 22 2005
a(n) = A030191(n-1), n > 0. - R. J. Mathar, Sep 05 2008
E.g.f.: 2*exp(5*x/2)*sinh(sqrt(5)*x/2)/sqrt(5). - Ilya Gutkovskiy, Aug 11 2017
From Kai Wang, Dec 22 2019: (Start)
a(n) = Sum_{i=0..n-1; j=0..n-1; i+2*j=n-1} 5^i*((i+j)!/(i!*j!)).
a(n*k)/a(k) = Sum_{i=0..n-1; j=0..n-1; i+2*j=n-1} (-1)^(j*(k-1))*b(k)^i*((i+j)!/(i!*j!)).
a((2*m+1)*k)/a(k) = Sum_{i=0..m-1} (-1)^(i*k)*A020876((2*m-2*i)*k) + 5^(m*k).
a(2*m*k)/a(k) = Sum_{i=0..m-1} (-1)^(i*k)*A020876((2*m-2*i-1)*k}.
a(m+r)*a(n+s) - a(m+s)*a(n+r) = -5^(n+s)*a(m-n)*a(r-s).
a(m+r)*a(n+s) + a(m+s)*a(n+r) = (2*A020876(m+n+r+s) - 5^(n+s)*A020876(m-n)*A020876(r-s))/5.
A020876(m+r)*A020876(n+s) - A020876(m+s)*A020876(n+r) = 5^(n+s+1)*a(m-n)*a(r-s).
A020876(m+r)*A020876(n+s) - 5*a(m+s)*a(n+r) = 5^(n+s)*A020876(m-n)*A020876(r-s).
A020876(m+r)*A020876(n+s) + 5*a(m+s)*a(n+r) = 2*A020876(m+n+r+s) + 5^(n+s+1)*a(m-n)*a(r-s).
a(n)^2 - a(n+1)*a(n-1) = 5^(n-1).
a(n)^2 - a(n+r)*a(n-r) = 5^(n-r)*a(r)^2.
a(m)*a(n+1) - a(m+1)*a(n) = 5^n*a(m-n).
a(m-n) = (a(m)*A020876(n) - A020876(m)*a(n))/(2*5^n).
a(m+n) = (a(m)*A020876(n) + A020876(m)*a(n))/2.
A020876(n)^2 - A020876(n+r)*A020876(n-r) = -5^(n-r+1)*a(r)^2.
A020876(m)*A020876(n+1) - A020876(m+1)*A020876(n) = -5^(n+1)*a(m-n).
A020876(m+n) - 5^(n)*A020876(m-n) = 5*a(m)*a(n).
A020876(m-n) = (A020876(m)*A020876(n) - 5*a(m)*a(n))/(2*5^n).
A020876(m+n) = (A020876(m)*A020876(n) + 5*a(m)*a(n))/2. (End)
a(2*n) = 5^n*Fibonacci(2*n), a(2*n+1) = 5^n*Lucas(2*n+1). - G. C. Greubel, Dec 27 2019
a(n) = Sum_{k=0..n} (-1)^(k+1)*binomial(2*n, n+k)*(k|5), where (k|5) is the Legendre symbol. - Greg Dresden, Oct 14 2022