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 11-16 of 16 results.

A098357 a(n) = A061017(n) - pi(n+1).

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 2, 2, 2, 2, 1, 2, 1, 2, 2, 2, 2, 2, 1, 2, 2, 2, 1, 2, 1, 1, 1, 2, 2, 3, 2, 2, 2, 2, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2, 3, 3
Offset: 1

Views

Author

David Applegate and N. J. A. Sloane, Oct 22 2008

Keywords

Comments

a(n) >= 0 for all n >= 1.
The old entry with this sequence number was a duplicate of A058071.

Crossrefs

A companion to A052511. Cf. A061017, A006218, A088526.

A100059 First differences of A052911.

Original entry on oeis.org

1, 5, 14, 45, 139, 434, 1351, 4209, 13110, 40837, 127203, 396226, 1234207, 3844441, 11975078, 37301261, 116189979, 361921042, 1127350583, 3511592833, 10938286998, 34071752661, 106130359315, 330586256610
Offset: 1

Views

Author

Gary W. Adamson, Oct 31 2004

Keywords

Comments

a(n)/a(n-1) tends to 3.11490754148...an eigenvalue of M and a root of the characteristic polynomial x^3 - 3x^2 - x + 2.

Examples

			a(5) = 139 = rightmost term in M^5 * [1 1 1] which is [434 205 139]. 434 = a(6), while 205 = A052911(5).
a(6) = 434 = 3*a(5) + a(4) - 2*a(3) = 3*139 + 45 - 2*14.
		

References

  • Boris A. Bondarenko, Generalized Pascal Triangles and Pyramids (in Russian), FAN, Tashkent, 1990, ISBN 5-648-00738-8.

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{3,1,-2},{1,5,14},30] (* Harvey P. Dale, Apr 21 2016 *)

Formula

G.f.: (2*x^2-2*x-1)*x / (-2*x^3+x^2+3*x-1).
Recurrence: a(n) = 3*a(n-1) + a(n-2) - 2*a(n-3).
a(n) = rightmost term in M^5 * [1 1 1], where M = the 3 X 3 upper triangular matrix [2 1 2 / 1 1 0 / 1 0 0].
INVERT transform of (1, 4, 5, 6, 7, 8, 9, ...) with offset 0.

Extensions

Edited by Ralf Stephan, Nov 02 2004

A250111 Number of orbits of size 2 in vertices of Fibonacci cube Gamma_n under the action of its automorphism group.

Original entry on oeis.org

1, 1, 1, 3, 4, 9, 13, 25, 38, 68, 106, 182, 288, 483, 771, 1275, 2046, 3355, 5401, 8811, 14212, 23112, 37324, 60580, 97904, 158717, 256621, 415715, 672336, 1088661, 1760997, 2850645, 4611642, 7463884, 12075526, 19541994, 31617520, 51163695, 82781215
Offset: 1

Views

Author

N. J. A. Sloane, Nov 19 2014

Keywords

Crossrefs

Programs

  • Magma
    [n eq 1 select 1 else (1/2)*(Fibonacci(n+2)-Fibonacci(Floor((n-(-1)^n)/2)+2)): n in [1..40]]; // Vincenzo Librandi, Nov 22 2014
    
  • Mathematica
    LinearRecurrence[{1,2,-1,0,-1,-1},{1,1,1,3,4,9,13},40] (* Harvey P. Dale, Feb 10 2018 *)
  • PARI
    a(n)=if(n==1,1,(fibonacci(n+2) - fibonacci((n-(-1)^n)\2+2))/2); \\ Joerg Arndt, Nov 22 2014
    
  • PARI
    Vec(x*(1-2*x^2+x^3+x^5+x^6)/((1-x-x^2)*(1-x^2-x^4)) + O(x^100)) \\ Colin Barker, Dec 01 2014
    
  • SageMath
    def A250111(n): return bool(n==1) + sum( fibonacci(j+1)*fibonacci(n-2*j-1) for j in (0..((n-1)//2)) )
    [A250111(n) for n in (1..50)] # G. C. Greubel, Apr 06 2022

Formula

a(n) = (1/2) * (F(n+2) - F(floor((n-(-1)^n)/2)+2)) for n >= 2, a(1)=1. - Joerg Arndt, Nov 22 2014
a(n) = a(n-1)+2*a(n-2)-a(n-3)-a(n-5)-a(n-6) for n>7. - Colin Barker, Dec 01 2014
G.f.: x*(1-2*x^2+x^3+x^5+x^6)/((1-x-x^2)*(1-x^2-x^4)). - Colin Barker, Dec 01 2014
From G. C. Greubel, Apr 06 2022: (Start)
a(n) = [n=1] + Sum_{k=0..floor((n-1)/2)} Fibonacci(k+1)*Fibonacci(n-2*k-1).
a(2*n) = (1/2)*(Fibonacci(2*n+2) - Fibonacci(n+1)), n >= 1.
a(2*n+1) = (1/2)*(Fibonacci(2*n+3) - Fibonacci(n+3) + 2*[n=0]), n >= 0. (End)

Extensions

More terms from Vincenzo Librandi, Nov 22 2014

A283845 Square array read by antidiagonals: T(1,1) = T(1,2) = T(2,1) = T(2,2) = 1; thereafter T(m,n) = min {T(m,n-2) + T(m,n-1), T(m-2,n) + T(m-1,n), T(m-2,n-2) + T(m-1,n-1)}.

Original entry on oeis.org

1, 1, 1, 2, 1, 2, 3, 2, 2, 3, 5, 3, 2, 3, 5, 8, 5, 3, 3, 5, 8, 13, 8, 5, 3, 5, 8, 13, 21, 13, 8, 5, 5, 8, 13, 21, 34, 21, 13, 8, 5, 8, 13, 21, 34, 55, 34, 21, 13, 8, 8, 13, 21, 34, 55, 89, 55, 34, 21, 13, 8, 13, 21, 34, 55, 89, 144, 89, 55, 34, 21, 13, 13, 21, 34, 55, 89, 144
Offset: 1

Views

Author

N. J. A. Sloane, Mar 31 2017

Keywords

Comments

A naive version of a two-dimensional Fibonacci array.
There should probably be another entry for the array which has offset 0 and starts with T(0,0) = 0, T(0,1) = T(1,0) = T(1,1) = 1.
See A058071 for a more interesting version.
T(n, 1) = T(n, n) = A000045(n) for n > 0. - Indranil Ghosh, Apr 01 2017

Examples

			The square array begins:
   1,  1,  2,  3,  5,  8, 13, 21, ...
   1,  1,  2,  3,  5,  8, 13, 21, ...
   2,  2,  2,  3,  5,  8, 13, 21, ...
   3,  3,  3,  3,  5,  8, 13, 21, ...
   5,  5,  5,  5,  5,  8, 13, 21, ...
   8,  8,  8,  8,  8,  8, 13, 21, ...
  13, 13, 13, 13, 13, 13, 13, 21, ...
  ...
The first few antidiagonals are:
   1;
   1, 1;
   2, 1, 2;
   3, 2, 2, 3;
   5, 3, 2, 3, 5;
   8, 5, 3, 3, 5, 8;
  13, 8, 5, 3, 5, 8, 13;
  ...
		

Crossrefs

Programs

  • Mathematica
    Table[Fibonacci[Max[m, n - m + 1]], {n, 20}, {m, n}] // Flatten (* Indranil Ghosh, Apr 01 2017 *)
  • PARI
    tabl(nn) = {for(n=1, nn, for(m=1, n, print1(fibonacci(max(m, n - m + 1)),", ");); print(););}
    tabl(20) \\ Indranil Ghosh, Apr 01 2017
    
  • Python
    from sympy import fibonacci
    for n in range(1, 21):
        print([fibonacci(max(m, n - m + 1)) for m in range(1, n + 1)]) # Indranil Ghosh, Apr 01 2017

Formula

T(m,n) = Fibonacci(k) where k = max(m,n).

Extensions

Extended by Indranil Ghosh, Apr 01 2017

A304726 a(n) = n^4 + 4*n^2 + 3.

Original entry on oeis.org

3, 8, 35, 120, 323, 728, 1443, 2600, 4355, 6888, 10403, 15128, 21315, 29240, 39203, 51528, 66563, 84680, 106275, 131768, 161603, 196248, 236195, 281960, 334083, 393128, 459683, 534360, 617795, 710648, 813603, 927368, 1052675, 1190280, 1340963, 1505528, 1684803
Offset: 0

Views

Author

Vincenzo Librandi, May 31 2018

Keywords

Comments

Alternating sum of all points on the fourth row of the Hosoya triangle composed of Fibonacci polynomials, where F_{0}(n) = 1 and F_{1}(n) = n, hence a(n) = F_{5}(n)/F_{1}(n) for n>0 (see Florez et al. reference, page 7, Table 4 and following sum).
Apart from 8, all terms belong to A217554 because a(n) = (n^2+1)^2 + (n+1)^2 + (n-1)^2 = (n^2+2)^2 - 1. - Bruno Berselli, Jun 04 2018

Crossrefs

Subsequence of A005563.

Programs

  • GAP
    List([0..40], n -> (n^2+2)^2-1); # Muniru A Asiru, Jun 03 2018
  • Magma
    [n^4+4*n^2+3: n in [0..40]];
    
  • Maple
    seq((n^2+2)^2-1,n=0..40); # Muniru A Asiru, Jun 03 2018
  • Mathematica
    Table[n^4 + 4 n^2 + 3, {n, 0, 35}]
    LinearRecurrence[{5,-10,10,-5,1},{3,8,35,120,323},40] (* Harvey P. Dale, Mar 04 2021 *)

Formula

G.f.: (3 - 7*x + 25*x^2 - 5*x^3 + 8*x^4)/(1-x)^5.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5).
a(n) = A059100(n)^2 - 1.
Sum_{n>=0} 1/a(n) = 1/6 + coth(Pi)*Pi/4 - coth(sqrt(3)*Pi)*Pi/(4*sqrt(3)). - Amiram Eldar, Feb 24 2023

A110361 A triangle of coefficients based on A000931 and A000045: a(n) = a(n - 2) + a(n - 3); t(n,m) := a(n - m + 1)*a(m + 1)*Fibonacci[(n - m + 1)]*Fibonacci[(m + 1)].

Original entry on oeis.org

1, 1, 1, 4, 1, 4, 6, 4, 4, 6, 15, 6, 16, 6, 15, 32, 15, 24, 24, 15, 32, 65, 32, 60, 36, 60, 32, 65, 147, 65, 128, 90, 90, 128, 65, 147, 306, 147, 260, 192, 225, 192, 260, 147, 306, 660, 306, 588, 390, 480, 480, 390, 588, 306, 660, 1424, 660, 1224, 882, 975, 1024, 975, 882
Offset: 1

Views

Author

Roger L. Bagula and Gary W. Adamson, Aug 24 2008

Keywords

Comments

Row sums are:
{1, 2, 9, 20, 58, 142, 350, 860, 2035, 4848, 11354}.

Examples

			{1},
{1, 1},
{4, 1, 4},
{6, 4, 4, 6},
{15, 6, 16, 6, 15},
{32, 15, 24, 24, 15, 32},
{65, 32, 60, 36, 60, 32, 65},
{147, 65, 128, 90, 90, 128, 65, 147},
{306, 147, 260, 192, 225, 192, 260, 147, 306},
{660, 306, 588, 390, 480, 480, 390, 588, 306, 660},
{1424, 660, 1224, 882, 975, 1024, 975, 882, 1224, 660, 1424}
		

Crossrefs

Programs

  • Mathematica
    Clear[t, a, n, m] a[0] = 1; a[1] = 1; a[2] = 1; a[n_] := a[n] = a[n - 2] + a[n - 3]; t[n_, m_] := a[(n - m + 1)]*a[(m + 1)]*Fibonacci[(n - m + 1)]*Fibonacci[(m + 1)]; Table[Table[t[n, m], {m, 0, n}], {n, 0, 10}]; Flatten[%]

Formula

a(n) = a(n - 2) + a(n - 3); t(n,m) := a(n - m + 1)*a(m + 1)*Fibonacci[(n - m + 1)]*Fibonacci[(m + 1)].
Previous Showing 11-16 of 16 results.