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.

Previous Showing 11-15 of 15 results.

A141448 Generalized Pell numbers P(n,5,5).

Original entry on oeis.org

0, 1, 2, 5, 13, 34, 89, 232, 605, 1578, 4116, 10736, 28003, 73041, 190515, 496926, 1296147, 3380779, 8818187, 23000741, 59993521, 156482896, 408159020, 1064613385, 2776862948, 7242974718, 18892067685, 49276745441, 128530009618
Offset: 0

Views

Author

R. J. Mathar, Aug 07 2008

Keywords

Comments

P(n,2,2) and P(n,2,1) are in A000129.
P(n,3,2) is A116413. P(n,3,1) and P(n,3,3) are A077939.
P(n,4,1) and P(n,4,4) are A103142.

Programs

  • Magma
    I:=[0,1,2,5,13]; [n le 5 select I[n] else 2*Self(n-1)+Self(n-2)+Self(n-3)+Self(n-4)+Self(n-5): n in [1..30]]; // Vincenzo Librandi, Dec 13 2012
  • Maple
    P := proc(n,k,i) option remember ; if n = 1-i then 1; elif n <= 0 then 0; else 2*P(n-1,k,i)+add(P(n-j,k,i),j=2..k) ; fi ; end: for n from 0 to 40 do printf("%d,",P(n,5,5)) ; od:
  • Mathematica
    CoefficientList[Series[x/(1 - 2*x - x^2 - x^3 - x^4 - x^5), {x, 0, 40}], x] (* Vincenzo Librandi, Dec 13 2012 *)
    LinearRecurrence[{2,1,1,1,1},{0,1,2,5,13},40] (* Harvey P. Dale, Jan 08 2016 *)
  • Maxima
    a(n):=b(n+1);
    b(n):=sum(sum(binomial(k,r)*2^(k-r)*sum((sum(binomial(j,-r+n-m-k-j)*binomial(m,j),j,0,m))*binomial(r,m),m,0,r),r,0,k),k,1,n); /* Vladimir Kruchinin, May 05 2011 */
    

Formula

From R. J. Mathar, Nov 28 2008: (Start)
a(n) = 2*a(n-1) + a(n-2) + a(n-3) + a(n-4) + a(n-5).
G.f.: x/(1-2*x-x^2-x^3-x^4-x^5). (End)
a(n+1) = Sum_(k=1..n, Sum_(r=0..k, binomial(k,r)*2^(k-r)*Sum_(m=0..r,(Sum_(j=0..m, binomial(j,-r+n-m-k-j)*binomial(m,j)))*binomial(r,m)))), a(0)=0, a(1)=1. [Vladimir Kruchinin, May 05 2011]

A276226 a(n+3) = 2*a(n+2) + a(n+1) + a(n) with a(0)=0, a(1)=6, a(2)=8.

Original entry on oeis.org

0, 6, 8, 22, 58, 146, 372, 948, 2414, 6148, 15658, 39878, 101562, 258660, 658760, 1677742, 4272904, 10882310, 27715266, 70585746, 179769068, 457839148, 1166033110, 2969674436, 7563221130, 19262149806, 49057195178, 124939761292, 318198867568, 810394691606, 2063928012072, 5256449583318, 13387221870314, 34094821336018
Offset: 0

Views

Author

G. C. Greubel, Aug 24 2016

Keywords

Crossrefs

Programs

  • Magma
    I:=[0,6,8]; [n le 3 select I[n] else 2*Self(n-1)+ Self(n-2)+Self(n-3): n in [1..40]]; // Vincenzo Librandi, Aug 25 2016
    
  • Mathematica
    LinearRecurrence[{2, 1, 1}, {0, 6, 8}, 50]
    CoefficientList[Series[2 (3 x - 2 x^2)/(1 - 2 x - x^2 - x^3), {x, 0, 33}], x] (* Michael De Vlieger, Aug 25 2016 *)
  • PARI
    concat(0, Vec(2*(3*x-2*x^2)/(1-2*x-x^2-x^3) + O(x^99))) \\ Altug Alkan, Aug 25 2016

Formula

Let p = (4*(61 + 9*sqrt(29)))^(1/3), q = (4*(61 - 9*sqrt(29)))^(1/3), and x = (1/6)*(4 + p + q) then x^n = (1/6)*(2*A276225(n) + a(n)*(p + q) + A077939(n-1)*(p^2 + q^2)).G.f.: 2*(3*x - 2*x^2)/(1 - 2*x - x^2 - x^3).

A276229 a(n+3) = -a(n+2) - 2*a(n+1) + a(n) with a(0)=0, a(1)=0, a(2)=1.

Original entry on oeis.org

0, 0, 1, -1, -1, 4, -3, -6, 16, -7, -31, 61, -6, -147, 220, 68, -655, 739, 639, -2772, 2233, 3950, -11188, 5521, 20805, -43035, 6946, 99929, -156856, -36056, 449697, -534441, -401009, 1919588, -1652011, -2588174, 7811784, -4287447, -13924295, 30310973
Offset: 0

Views

Author

G. C. Greubel, Aug 24 2016

Keywords

Comments

Essentially the same as A077978. - Georg Fischer, Oct 02 2018

Crossrefs

Programs

  • Magma
    I:=[0,0,1]; [n le 3 select I[n] else -Self(n-1)- 2*Self(n-2)+Self(n-3): n in [1..40]]; // Vincenzo Librandi, Aug 25 2016
    
  • Mathematica
    LinearRecurrence[{-1, -2, 1}, {0, 0, 1}, 50]
    CoefficientList[Series[x^2/(1 + x + 2 x^2 - x^3), {x, 0, 39}], x] (* Michael De Vlieger, Aug 25 2016 *)
  • PARI
    concat([0, 0], Vec(x^2/(1+x+2*x^2-x^3) + O(x^99))) \\ Altug Alkan, Aug 25 2016

Formula

G.f.: x^2/(1 + x + 2*x^2 - x^3).
Let P = (b-c)*(b-d), Q = (c-b)*(b-d), R = (d-b)*(d-c), (b, c, d) be the three roots of x^3 = 2*x^2 + x + 1, then a(n) = P^(-1)*b^(1-n) + Q^(-1)*c^(1-n) + R^(-1)*d^(1-n).
a(2*n) = -3*a(2*n-2) - 6*a(2*n-4) + a(2*n-6).

A375821 Number of ways to tile a 3-row parallelogram of length n with triangular and rectangular tiles, each of size 3.

Original entry on oeis.org

1, 1, 2, 7, 17, 41, 107, 274, 693, 1766, 4504, 11465, 29194, 74364, 189391, 482327, 1228412, 3128559, 7967841, 20292639, 51681711, 131623900, 335222103, 853749852, 2174345752, 5537663377, 14103422348, 35918853952, 91478793557, 232979863277, 593357374262
Offset: 0

Views

Author

Greg Dresden and Mingjun Oliver Ouyang, Aug 30 2024

Keywords

Comments

Here is the 3-row parallelogram of length 6 (with 18 cells):
_ ___ _ ___ _ ___
| | | | | | |
|__|___|_|___| |___|
| | | | | | |
|__|___|_|___| |___|
| | | | | | |
|_|___|_|___|_|___|,
and here are the two types of (triangular and rectangular) tiles of size 3, which can be rotated as needed:
_
| |
| | | | | | |
|_|___|, |_|___|_|.
As an example, here is one of the a(6) = 107 ways to tile the 3 x 6 parallelogram:
_ _______ _________
| | | |
| | | | |
| | |_|___________|
| | | |
|_|_______|_________|.

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{2, 0, 4, -1, 0, -1}, {1, 1, 2, 7, 17, 41}, 40]

Formula

a(n) = 2*a(n-1) + 4*a(n-3) - a(n-4) - a(n-6).
G.f.: (1 - x - x^3)/((1 + x^2 - x^3)*(1 - 2*x - x^2 - x^3)).
a(n) = (A077939(n) + A077961(n))/2.

A375823 Number of ways to tile a 3-row trapezoid of average length n with triangular and rectangular tiles, each of size 3.

Original entry on oeis.org

0, 1, 3, 6, 16, 43, 107, 271, 695, 1769, 4499, 11464, 29202, 74360, 189382, 482339, 1228417, 3128538, 7967848, 20292665, 51681683, 131623881, 335222157, 853749843, 2174345679, 5537663440, 14103422412, 35918853816, 91478793556, 232979863477, 593357374127
Offset: 0

Views

Author

Greg Dresden and Mingjun Oliver Ouyang, Aug 30 2024

Keywords

Comments

Here is the 3-row trapezoid of average length 6 (with 18 cells):
_ ___ _ ___ _
| | | | | |
|__|___|_|___| |_
| | | | | | |
|__|___|_|___| |___|_
| | | | | | | |
|_|___|_|___|_|___|_|,
and here are the two types of (triangular and rectangular) tiles of size 3, which can be rotated as needed:
_
| |
| | | | | | |
|_|___|, |_|___|_|.
As an example, here is one of the a(6) = 107 ways to tile the 3-row trapezoid
| | | |
| | | | | |
| | | | | |
| | | | | |
|_|_______|_|___|_____|.

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{2, 0, 4, -1, 0, -1}, {0, 1, 3, 6, 16, 43}, 40]

Formula

a(n) = 2*a(n-1) + 4*a(n-3) - a(n-4) - a(n-6).
G.f.: x*(1 + x)/((1 + x^2 - x^3)*(1 - 2*x - x^2 - x^3)).
a(n) = (A077939(n) - A077961(n))/2.
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