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 1-5 of 5 results.

A048577 Pisot sequence L(3,4).

Original entry on oeis.org

3, 4, 6, 9, 14, 22, 35, 56, 90, 145, 234, 378, 611, 988, 1598, 2585, 4182, 6766, 10947, 17712, 28658, 46369, 75026, 121394, 196419, 317812, 514230, 832041, 1346270, 2178310, 3524579, 5702888, 9227466, 14930353, 24157818, 39088170, 63245987, 102334156, 165580142
Offset: 0

Views

Author

Keywords

Crossrefs

Subsequence of A001611. See A008776 for definitions of Pisot sequences.

Programs

Formula

a(n) = Fib(n+3)+1. a(n) = 2a(n-1) - a(n-3).
a(n) = A020706(n-1), n>0. [From R. J. Mathar, Oct 15 2008]
G.f.: (3-2*x-2*x^2)/((1-x)*(1-x-x^2)). [Colin Barker, Apr 16 2012]

A020717 Pisot sequences L(6,9), E(6,9).

Original entry on oeis.org

6, 9, 14, 22, 35, 56, 90, 145, 234, 378, 611, 988, 1598, 2585, 4182, 6766, 10947, 17712, 28658, 46369, 75026, 121394, 196419, 317812, 514230, 832041, 1346270, 2178310, 3524579, 5702888, 9227466, 14930353, 24157818, 39088170, 63245987, 102334156, 165580142
Offset: 0

Views

Author

Keywords

References

  • Shalosh B. Ekhad, N. J. A. Sloane and Doron Zeilberger, Automated Proof (or Disproof) of Linear Recurrences Satisfied by Pisot Sequences, Preprint, 2016.

Crossrefs

Subsequence of A001611, A048577.
See A008776 for definitions of Pisot sequences.
Pairwise sums of A018910.

Programs

  • Mathematica
    Table[Fibonacci[n + 5] + 1, {n, 0, 36}] (* Michael De Vlieger, Jul 27 2016 *)
  • PARI
    pisotE(nmax, a1, a2) = {
      a=vector(nmax); a[1]=a1; a[2]=a2;
      for(n=3, nmax, a[n] = floor(a[n-1]^2/a[n-2]+1/2));
      a
    }
    pisotE(50, 6, 9) \\ Colin Barker, Jul 27 2016

Formula

a(n) = Fibonacci(n+5)+1 = A001611(n+5).
a(n) = 2*a(n-1) - a(n-3).
a(n) = A020706(n+1). - R. J. Mathar, Oct 25 2008

A226271 Index of 1/n in the Fibonacci (or rabbit) ordering of the positive rationals.

Original entry on oeis.org

1, 4, 6, 9, 14, 22, 35, 56, 90, 145, 234, 378, 611, 988, 1598, 2585, 4182, 6766, 10947, 17712, 28658, 46369, 75026, 121394, 196419, 317812, 514230, 832041, 1346270, 2178310, 3524579, 5702888, 9227466, 14930353, 24157818, 39088170, 63245987, 102334156, 165580142
Offset: 1

Views

Author

M. F. Hasler, Jun 01 2013

Keywords

Comments

The Fibonacci ordering of the rationals (cf. A226080) is the sequence of rationals produced from the initial vector [1] by appending iteratively the new rationals obtained by applying the map t-> (t+1, 1/t) to the vector (cf. example).
Apart from initial terms, the same as A001611=(1, 2, 2, 3, 4, 6,...), A020706=(4,6,9,...), A048577=(3, 4, 6, ...), A000381=(2, 3, 4, ...).

Examples

			Starting from the vector [1] and applying the map t->(1+t,1/t), we get [2,1] (but ignore the number 1 which already occurred earlier), then [3,1/2], then [4,1/3,3/2,2] (where we ignore 2), etc. This yields the sequence (1,2,3,1/2,4,1/3,3/2,5,1/4,4/3,5/2,2/3,....) The unit fractions 1=1/1, 1/2, 1/3, ... occur at positions 1,4,6,9,...
		

Programs

  • Mathematica
    LinearRecurrence[{2,0,-1},{1,4,6,9},40] (* Harvey P. Dale, Feb 04 2016 *)
  • PARI
    A226271(n)=if(n>1,fibonacci(n+2))+1
    
  • PARI
    {k=1;print1(s=1,",");U=Set(g=[1]);for(n=1,9,U=setunion(U,Set(g=select(f->!setsearch(U,f), concat(apply(t->[t+1,k/t],g))))); for(i=1,#g,numerator(g[i])==1&&print1(s+i","));s+=#g)} \\ for illustrative purpose
    
  • PARI
    Vec(-x*(2*x^3+2*x^2-2*x-1)/((x-1)*(x^2+x-1)) + O(x^50)) \\ Colin Barker, May 11 2016

Formula

a(n) = 2*a(n-1)-a(n-3) for n>4. G.f.: -x*(2*x^3+2*x^2-2*x-1) / ((x-1)*(x^2+x-1)). - Colin Barker, Jun 03 2013
a(n) = 1+(2^(-1-n)*((1-sqrt(5))^n*(-3+sqrt(5))+(1+sqrt(5))^n*(3+sqrt(5))))/sqrt(5) for n>1. - Colin Barker, May 11 2016
E.g.f.: -2*(1 + x) + exp(x) + (3*sqrt(5)*sinh(sqrt(5)*x/2) + 5*cosh(sqrt(5)*x/2))*exp(x/2)/5. - Ilya Gutkovskiy, May 11 2016

A277084 Pisot sequence L(4,14).

Original entry on oeis.org

4, 14, 49, 172, 604, 2122, 7456, 26198, 92052, 323444, 1136489, 3993295, 14031289, 49301911, 173232725, 608689936, 2138761243, 7514991434, 26405516950, 92781386582, 326007088306, 1145495077635, 4024940008834, 14142480741305, 49692606865991, 174605518105877
Offset: 0

Views

Author

Ilya Gutkovskiy, Sep 29 2016

Keywords

Comments

There is no simple g.f. - Ilya Gutkovskiy, May 23 2019

Crossrefs

Cf. A008776 for definitions of Pisot sequences.
Cf. A010904 (Pisot sequence E(4,14)), A251221 (seems to be Pisot sequence P(4,14)).

Programs

  • Mathematica
    RecurrenceTable[{a[0] == 4, a[1] == 14, a[n] == Ceiling[a[n - 1]^2/a[n - 2]]}, a, {n, 25}]

Formula

a(n) = ceiling(a(n-1)^2/a(n-2)), a(0) = 4, a(1) = 14.

A301791 Number of 2Xn 0..1 arrays with every element equal to 0 or 1 horizontally or antidiagonally adjacent elements, with upper left element zero.

Original entry on oeis.org

2, 5, 6, 9, 14, 22, 35, 56, 90, 145, 234, 378, 611, 988, 1598, 2585, 4182, 6766, 10947, 17712, 28658, 46369, 75026, 121394, 196419, 317812, 514230, 832041, 1346270, 2178310, 3524579, 5702888, 9227466, 14930353, 24157818, 39088170, 63245987
Offset: 1

Views

Author

R. H. Hardin, Mar 26 2018

Keywords

Comments

Row 2 of A301790.

Examples

			Some solutions for n=5
..0..0..1..0..0. .0..1..0..0..1. .0..1..0..1..1. .0..1..0..0..1
..1..0..1..1..0. .0..1..1..0..0. .0..1..0..0..1. .0..1..1..0..1
		

Crossrefs

Formula

Empirical: a(n) = 2*a(n-1) -a(n-3) for n>5.
Showing 1-5 of 5 results.