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 1-3 of 3 results.

A049681 a(n) = (Lucas(2*n) - Lucas(n))/2.

Original entry on oeis.org

0, 1, 2, 7, 20, 56, 152, 407, 1080, 2851, 7502, 19702, 51680, 135461, 354902, 929567, 2434320, 6374236, 16689752, 43697227, 114405500, 299525051, 784179002, 2053027082, 5374926720, 14071792681
Offset: 0

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Author

Keywords

Comments

Create a triangle with T(n,1) = L(n-1) for L a Lucas number and the other side T(n,n) = L(2*(n-1)). Interior elements are defined as T(r,c) = T(r-1,c-1) + T(r-1,c). Half the sum of the terms in row(n)=a(n) for n=1,2,3... - J. M. Bergot, Dec 15 2012

Crossrefs

Programs

  • GAP
    List([0..30], n-> (Lucas(1,-1,2*n)[2] - Lucas(1,-1,n)[2])/2 ); # G. C. Greubel, Dec 15 2019
  • Magma
    [(Lucas(2*n) - Lucas(n))/2: n in [0..30]]; // G. C. Greubel, Dec 02 2017
    
  • Maple
    Lucas:= n -> combinat:-fibonacci(n+1)+combinat:-fibonacci(n-1):
    seq((Lucas(2*n)-Lucas(n))/2,n=0..100); # Robert Israel, Sep 15 2016
  • Mathematica
    Table[(LucasL[2n] - LucasL[n])/2, {n, 0, 20}] (* Vladimir Reshetnikov, Sep 15 2016 *)
  • PARI
    x='x+O('x^30); concat([0], Vec(x*(1-2*x+2*x^2)/((1-x-x^2)*(1-3*x+x^2)) )) \\ G. C. Greubel, Dec 02 2017
    
  • Sage
    [(lucas_number2(2*n,1,-1) - lucas_number2(n,1,-1))/2 for n in (0..30)] # G. C. Greubel, Dec 15 2019
    

Formula

G.f.: x*(1-2*x+2*x^2)/( (1-x-x^2)*(1-3*x+x^2) ). - R. J. Mathar, Dec 17 2012
a(n) = Lucas(n)*(Lucas(n) - 1)/2 - (-1)^n = binomial(Lucas(n), 2) - (-1)^n. - Vladimir Reshetnikov, Sep 27 2016
E.g.f.: (1/2)*exp(-2*x/(1+sqrt(5)))*(-1 + exp(x))*(1 + exp(sqrt(5)*x)). - Stefano Spezia, Dec 15 2019

Extensions

Corrected by Franklin T. Adams-Watters, Oct 25 2006
Corrected by T. D. Noe, Nov 01 2006

A362067 Sum of successive Fibonacci numbers F(n) : a(n) = Sum_{k = 0..n} F(n+k).

Original entry on oeis.org

0, 2, 6, 18, 50, 136, 364, 966, 2550, 6710, 17622, 46224, 121160, 317434, 831430, 2177322, 5701290, 14927768, 39083988, 102327390, 267903350, 701391022, 1836283246, 4807480608, 12586194000, 32951158706, 86267374854, 225851115906, 591286215650, 1548007923880
Offset: 0

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Author

Philippe Deléham, Apr 07 2023

Keywords

Examples

			a(n) are the row sums of the triangle T(n,k) (A199334):
  0;
  1, 1;
  1, 2,  3;
  2, 3,  5,  8;
  3, 5,  8, 13, 21;
  5, 8, 13, 21, 34, 55;
  ...
T(n,k) = T(n,k-1) + T(n-1, k-1); T(n,0) = A000045(n).
		

Crossrefs

Programs

  • Mathematica
    A362067[n_] := Fibonacci[n+1]*(LucasL[n+1] - 1); Array[A362067, 50, 0] (* or *)
    LinearRecurrence[{4, -3, -2, 1}, {0, 2, 6, 18}, 50] (* Paolo Xausa, Jun 10 2024 *)

Formula

a(n) = 4*a(n-1)-3*a(n-2)-2*a(n-3)+a(n-4), a(0)=0, a(1)=2, a(2)=6, a(3)=18.
G.f.: 2*x*(1-x)/((1-3*x+x^2)*(1-x-x^2)).
a(n) = A000045(2n+2) - A000045(n+1).
a(n) = 2 * A094292(n+1). - Alois P. Heinz, Apr 07 2023
a(n) = A000045(n+1)*(A000032(n+1) - 1). - Paolo Xausa, Jun 10 2024

A327917 Triangle T read by rows: T(k, n) = A(k-n, k) with the array A(k, n) = F(2*k+n) = A000045(2*k+n), for k >= 0 and n >= 0.

Original entry on oeis.org

0, 1, 1, 3, 2, 1, 8, 5, 3, 2, 21, 13, 8, 5, 3, 55, 34, 21, 13, 8, 5, 144, 89, 55, 34, 21, 13, 8, 377, 233, 144, 89, 55, 34, 21, 13, 987, 610, 377, 233, 144, 89, 55, 34, 21, 2584, 1597, 987, 610, 377, 233, 144, 89, 55, 34, 6765, 4181, 2584, 1597, 987, 610, 377, 233, 144, 89, 55
Offset: 0

Views

Author

Wolfdieter Lang, Oct 06 2019

Keywords

Comments

This is the row reversed triangle A199334.
This is the analog of the array and the triangle A327916, where the positive odd numbers instead of the Fibonacci numbers are used.
The array A arises from the following Pascal-type triangles PF(k), for k >= 0, based on A000045 (Fibonacci). For example, the Pascal type triangle PF(k), for k = 3 is
0 1 1 2
1 2 3
3 5
8
For k -> infinity the left-aligned row sequences build the array A(k, n), with k >= 0 and n >= 0, that is, A(k, n) = F(2*k + n). See the example section for the first rows of A.
The triangle T is the array A read by upwards antidiagonals.

Examples

			The Array A(k, n) begins:
k\n  0  1   2   3   4   5 ...
-----------------------------
0:   0  1   1   2   3   5 ...   F(n)
1:   1  2   3   5   8  13 ...   F(n+2)
2:   3  5   8  13  21  34 ...   F(n+4)
3:   8 13  21  34  55  89 ...   F(n+6)
4:  21 34  55  89 144 233 ...   F(n+8)
5:  55 89 144 233 377 610 ...   F(n+10)
...
---------------------------------------
The triangle T(k, n) begins:
k\n     0    1    2    3   4   5   6   7   8  9 10 ...
------------------------------------------------------
0:      0
1:      1    1
2:      3    2    1
3:      8    5    3    2
4:     21   13    8    5   3
5:     55   34   21   13   8   5
6:    144   89   55   34  21  13   8
7:    377  233  144   89  55  34  21  13
8:    987  610  377  233 144  89  55  34  21
9:   2584 1597  987  610 377 233 144  89  55 34
10:  6765 4181 2584 1597 987 610 377 233 144 89 55
...
		

Crossrefs

Cf. A000045, A199334 (row reversed), A001906, A327916.
Column sequences of T (no leading zeros) and A: from the shifted Fibonacci bisection {F(2*k) = A001906(k)} for even n, and {F(2*k+1) = A001519(k+1)}, for odd n.
Row sums: 2*A094292(n+1) = F(2*(n+1)) - F(n+1), n >= 0.
Alternating row sums: 2*A164267(n-1), n >= 0, with 0 for n = 0.

Formula

A(k, n) = Sum_{j=0..k} binomial(k, j)*F(n+j) = F(2*k+n), for k >= 0 and n >= 0.
T(k, n) = A(k - n, n) = F(2*k - n), for k >= 0 and n = 0..k, with the Fibonacci numbers F = A000045.
Recurrence: T(k,0) = F(2*k), k >= 0, T(k, n) = T(k, n-1) - T(k-1, n-1), k >= 1, n = 1..k, and T(k, n) = 0 if k < n.
O.g.f. for row polynomials R(n, x) = Sum_{n=0..k} T(k, n)*x^n:
G(x, z) = Sum_{n=0} R(n, x)*z^n = z*(1 + x - 2*x*z)/((1 - 3*z + z^2)*(1 - x*z - (x*z)^2)).
T(k, 0) = Sum_{n=0..k} binomial(k,n)*T(n, n), k >= 0 (binomial transform).
Showing 1-3 of 3 results.