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.

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A093730 Antidiagonal sums of triangle A093729, which enumerates the number of nodes in the tree of tournament sequences.

Original entry on oeis.org

1, 1, 2, 5, 18, 102, 949, 14731, 386060, 17323052, 1351157580, 185867701560, 45682244004244, 20283964291276804, 16423005586691362832, 24434416299840231799694, 67236458264587977465709983
Offset: 0

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Author

Paul D. Hanna, Apr 14 2004

Keywords

Comments

Related to A008934 (the number of tournament sequences).

Crossrefs

Programs

  • Mathematica
    T[n_, k_] := T[n, k] = If[n<0, 0, If[n==0, 1, If[k==0, 0, If[k<=n, T[n, k-1] - T[n-1, k] + T[n-1, 2*k-1] + T[n-1, 2*k], Sum[(-1)^(j-1) * Binomial[n+1, j]*T[n, k-j], {j, 1, n+1}]]]]]; a[n_] := Sum[T[n-k, k], {k, 0, n}]; Table[a[n], {n, 0, 16}] (* Jean-François Alcover, Oct 06 2016, translated from PARI *)
  • PARI
    {T(n,k)=if(n<0,0,if(n==0,1,if(k==0,0, if(k<=n,T(n,k-1)-T(n-1,k)+T(n-1,2*k-1)+T(n-1,2*k), sum(j=1,n+1, (-1)^(j-1)*binomial(n+1,j)*T(n,k-j))))))}
    a(n)=sum(k=0,n,T(n-k,k))
    
  • SageMath
    @CachedFunction
    def T(n, k): # T = A093729
        if n<0: return 0
        elif n==0: return 1
        elif k==0: return 0
        elif kA093730(n): return sum(T(n-k,k) for k in range(n+1))
    [A093730(n) for n in range(31)] # G. C. Greubel, Feb 22 2024

Formula

a(n) = Sum_{k=0..n} A093729(n-k, k).

A097711 Column 1 of triangle A097710, in which row (n) is formed from the sums of the adjacent terms in row (n-1) of the matrix square of A097710.

Original entry on oeis.org

1, 3, 13, 88, 951, 16691, 484490, 23701698, 1990327810, 291750344191, 75757923092106, 35286335933354828, 29791358931890967248, 45989706937220594708463, 130760311958838053647976497
Offset: 0

Views

Author

Paul D. Hanna, Aug 22 2004

Keywords

Comments

Related to the number of tournament sequences (A008934).

Crossrefs

Programs

  • Mathematica
    T[n_, k_]:= T[n, k]= If[n<0 || k>n, 0, If[n==k, 1, If[k==0, Sum[T[n-1, j]*T[j,0], {j,0,n-1}], Sum[T[n-1,j]*(T[j,k-1] +T[j,k]), {j,0,n-1}] ]]]; (* T = A097710 *)
    A097711[n_]:= T[n+1,1];
    Table[A097711[n], {n,0,30}] (* G. C. Greubel, Feb 21 2024 *)
  • SageMath
    @CachedFunction
    def T(n, k): # T = A097710
        if n< 0 or k<0 or k>n: return 0
        elif k==n: return 1
        elif k==0: return sum(T(n-1,j)*T(j,0) for j in range(n))
        else: return sum(T(n-1, j)*(T(j, k-1)+T(j,k)) for j in range(n))
    def A097711(n): return T(n+1,1)
    [A097711(n) for n in range(31)] # G. C. Greubel, Feb 21 2024

A113080 Square table, read by antidiagonals, where T(n,k) equals the number of k-tournament sequences of length n for k>=1, with T(0,k) = 1 for k>=1 and T(n,1) = 0 for n>0.

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 2, 2, 1, 0, 7, 10, 3, 1, 0, 41, 114, 27, 4, 1, 0, 397, 2970, 693, 56, 5, 1, 0, 6377, 182402, 52812, 2704, 100, 6, 1, 0, 171886, 27392682, 12628008, 481376, 8125, 162, 7, 1, 0, 7892642, 10390564242, 9924266772, 337587520, 2918750, 20502, 245, 8
Offset: 1

Views

Author

Paul D. Hanna, Oct 14 2005

Keywords

Comments

A k-tournament sequence is an increasing sequence of positive integers (t_1,t_2,...) such that t_1 = p, t_i = p (mod k-1) and t_{i+1} <= k*t_i, where k>1, p>=1. This is the table of k-tournament sequences when the starting node has label p = 1 for k>=1.

Examples

			Table begins:
1,1,1,1,1,1,1,1,1,1,1,1,1,...
0,1,2,3,4,5,6,7,8,9,10,11,...
0,2,10,27,56,100,162,245,352,486,650,...
0,7,114,693,2704,8125,20502,45619,92288,173259,...
0,41,2970,52812,481376,2918750,13399506,50216915,...
0,397,182402,12628008,337587520,4976321250,48633051942,...
0,6377,27392682,9924266772,978162377600,42197834315625,...
0,171886,10390564242,26507035453923,12088945462984960,...
0,7892642,10210795262650,246323730279500082,...
		

Crossrefs

Columns: A008934 (k=2), A113089 (k=3), A113100 (k=4), A113113 (k=5); related tables: A093729 (k=2), A113081 (k=3), A113092 (k=4), A113103 (k=5).

Programs

  • PARI
    {T(n,k)=local(M=matrix(n+1,n+1));for(r=1,n+1, for(c=1,r, M[r,c]=if(r==c,1,if(c>1,(M^k)[r-1,c-1])+(M^k)[r-1,c]))); return((M^(k-1))[n+1,1])}

A137273 Number of partitions of n-th Fibonacci number into Fibonacci parts obtained by iteratively dividing F(k) into F(n-1) and F(n-2); number of sub-Fibonacci sequences of length n starting with 1,0.

Original entry on oeis.org

1, 1, 2, 3, 6, 13, 37, 134, 659, 4416, 41343, 546577, 10345970, 283128770, 11306821624, 664047579721, 57753201767477, 7483309752358051
Offset: 1

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Author

Keywords

Comments

By a sub-Fibonacci sequence we mean a sequence of nonnegative integers b(i) with b(i) <= b(i-1) + b(i-2). Here we are taking b(1) = 1 and b(2) = 0.
In the above, b(i) (for i >= 2) is the number of times F(n-i+2) is divided into the next two smaller Fibonacci numbers in forming the partition.

Examples

			For the sub-Fibonacci sequence 1,0,1,1,1,2, we split F(6)=8 into 5,3; split the 5 into 3,2; split one 3 into 2,1; and split both 2's into 1,1. This gives the partition [3,1^5].
[2^4] is the smallest partition of a Fibonacci number into Fibonacci parts that cannot be obtained in this way.
		

Crossrefs

Programs

  • PARI
    nextfibpart(m) = local(s); s=matsize(m);matrix(s[2],s[1]+s[2]-1,i,j,sum(k=max(j-i+1,1),s[1],m[k,i]))
    alist(n) = {local(v,m); v=vector(n,j,1); m=[0;1]; for(i=3,n, m=nextfibpart(m);v[i]=sum(j=1,matsize(m)[1],sum(k=1,matsize(m)[2],m[j,k]))); v}

A355129 a(n) is the number of integer sequences b(0..n) of length n+1, with 0 <= b(k) <= k! and monotonic b(k) <= b(k+1).

Original entry on oeis.org

2, 3, 7, 40, 856, 91821, 60080136, 279276911843, 10503211888973754, 3585680755683196123365, 12323227994417456429490342865, 468378989392773003347310901356953089, 214565221409985003242070442557341938941878313, 1282499669290042152350268651085002913530161723080398635
Offset: 0

Views

Author

Thomas Scheuerle, Aug 04 2022

Keywords

Comments

List of the possible cases regarding the patterns of the numbers in the sequence b:
Length: 1 2 3 4 5 6
Pos 0: 1 1 1 1 1 1
Pos 1: 1 2 3 4 5 6
Pos 2: 0 0 3 7 12 18
Pos 3: 0 0 0 7 19 37
Pos 4: 0 0 0 7 26 63
Pos 5: 0 0 0 7 33 96
Pos 6: 0 0 0 7 40 136
Pos 7: 0 0 0 0 40 176
Pos 8: 0 0 0 0 40 216
... ... ... ... ... ... ...
Sum: 2 3 7 40 856 91821
Each row counts the number of possible distributions of numbers, row "Pos 0" is the number of possible distributions with only the number zero. The row "Pos 1" counts the distributions of zeros and ones. The row "Pos 2" the possible distributions of {0,1,2} and so forth.
From top to down: If a number in the column length = k has reached the value of the sum of the column length = k-1, this number will be k!-(k-1)!+1 times repeated. Before this limit is reached each number is the sum of the neighbor one step above and the neighbor one step to the left.

Examples

			For a(0) we get two possible sequences:
  {0}, {1}.
For a(1) we get three possible sequences:
  {0, 0}, {0, 1}, {1, 1}.
For a(2) = 7 we get:
  {0, 0, 0}, {0, 0, 1}, {0, 0, 2}, {0, 1, 1},
  {0, 1, 2}, {1, 1, 1}, {1, 1, 2}.
		

Crossrefs

Cf. A000108 (if we change the definition into 0 <= b(k) <= k).

Programs

  • PARI
    a(n) = binomial((n-1)! + n-1, n-1) + binomial((n-1)! + n-2, n-1) + sum(r = 1, n-2, sum(k = 0, r-1 ,binomial((n-1)! - r! - k+n - 2, n-1)*binomial(r-1,k)*a(r)*(-1)^(k+1)))

Formula

a(n) = binomial((n-1)! + n-1, n-1) + binomial((n-1)! + n-2, n-1) + Sum_{r = 1..n-2} Sum_{k = 0..r-1} binomial((n-1)! - r! - k+n - 2, n-1)*binomial(r-1,k)*a(r)*(-1)^(k+1).
Previous Showing 21-25 of 25 results.