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 1-10 of 11 results. Next

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

A008934 Number of tournament sequences: sequences (a_1, a_2, ..., a_n) with a_1 = 1 such that a_i < a_{i+1} <= 2*a_i for all i.

Original entry on oeis.org

1, 1, 2, 7, 41, 397, 6377, 171886, 7892642, 627340987, 87635138366, 21808110976027, 9780286524758582, 7981750158298108606, 11950197013167283686587, 33046443615914736611839942, 169758733825407174485685959261, 1627880269212042994531083889564192
Offset: 0

Views

Author

Mauro Torelli (torelli(AT)hermes.mc.dsi.unimi.it), Jeffrey Shallit

Keywords

Comments

Also number of Meeussen sequences of length n (see the Cook-Kleber reference).
Column 1 of triangle A093729. Also generated by the iteration procedure that constructs triangle A093654. - Paul D. Hanna, Apr 14 2004
a(n) is the number of sequences (u_1,u_2,...,u_n) of positive integers such that u_1=1 and u_i <= 1+ u_1+...+u_{i-1} for 2<=i<=n. For example, omitting parentheses and commas, a(3)=7 counts 111, 112, 113, 121, 122, 123, 124. The difference-between-successive-terms operator is a bijection from the title sequences to these sequences. For example, the tournament sequence (1, 2, 4, 5, 9, 16) bijects to (1,2,1,4,7). (To count tournament sequences by length, the offset should be 1.) - David Callan, Oct 31 2020

Examples

			The 7 tournament sequences of length 4 are 1234, 1235, 1236, 1245, 1246, 1247, 1248.
		

Crossrefs

Forms column 0 of triangle A097710.

Programs

  • Mathematica
    t[n_?Negative, ] = 0; t[0, ] = 1; t[, 0] = 0; t[n, k_] /; k <= n :=  t[n, k] = t[n, k-1] - t[n-1, k] + t[n-1, 2k-1] + t[n-1, 2 k]; t[n_, k_] /; k > n :=  t[n, k] =Sum[(-1)^(j-1) Binomial[n+1, j]*t[n, k-j] , {j, 1, n+1}]; Table[t[n, 1], {n, 0, 15} ] (* Jean-François Alcover, May 17 2011, after PARI prog. *)
  • 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))))))} /*(Cook-Kleber)*/ a(n)=T(n,1)
    
  • SageMath
    @CachedFunction
    def T(n, k):
        if n<0: return 0
        elif n==0: return 1
        elif k==0: return 0
        elif kA008934(n): return T(n,1)
    [A008934(n) for n in range(31)] # G. C. Greubel, Feb 22 2024

Formula

From Paul D. Hanna, Apr 14 2004: (Start)
a(n) = A093729(n, 1).
a(n) = A093655(2^n). (End)
a(n) = A097710(n, 0). - Paul D. Hanna, Aug 24 2004
From Benedict W. J. Irwin, Nov 26 2016: (Start)
Conjecture: a(n) is given by a series of nested sums as follows:
a(2) = Sum_{i=1..2} 1,
a(3) = Sum_{i=1..2} Sum_{j=1..i+2} 1,
a(4) = Sum_{i=1..2} Sum_{j=1..i+2} Sum_{k=1..i+j+2} 1,
a(5) = Sum_{i=1..2} Sum_{j=1..i+2} Sum_{k=1..i+j+2} Sum_{l=1..i+j+k+2} 1.
(End)

A113106 Triangle T, read by rows, that satisfies the recurrence: T(n,k) = [T^5](n-1,k-1) + [T^5](n-1,k) for n>k>=0, with T(n,n)=1 for n>=0, where T^5 is the matrix 5th power of T.

Original entry on oeis.org

1, 1, 1, 5, 6, 1, 85, 115, 31, 1, 4985, 7420, 2590, 156, 1, 1082905, 1744965, 723370, 62090, 781, 1, 930005021, 1601759426, 752616215, 82390620, 1532715, 3906, 1, 3306859233805, 6024941167511, 3117415999361, 409321203715, 10025307495
Offset: 0

Views

Author

Paul D. Hanna, Oct 14 2005

Keywords

Comments

Column 0 of the matrix power p, T^p, equals the number of 5-tournament sequences having initial term p (see A113103 for definitions).

Examples

			Triangle begins:
1;
1,1;
5,6,1;
85,115,31,1;
4985,7420,2590,156,1;
1082905,1744965,723370,62090,781,1;
930005021,1601759426,752616215,82390620,1532715,3906,1;
Matrix 4th power T^4 (A113112) begins:
1;
4,1;
56,24,1;
2704,1576,124,1;
481376,346624,39376,624,1; ...
where column 0 equals A113113.
Matrix 5th power T^5 (A113114) begins:
1;
5,1;
85,30,1;
4985,2435,155,1;
1082905,662060,61310,780,1;
930005021,671754405,80861810,1528810,3905,1; ...
where adjacent sums in row n of T^5 forms row n+1 of T.
		

Crossrefs

Cf. A097710, A113084, A113095; A113103, A113107 (column 0), A113108 (T^2), A113110 (T^3), A113112 (T^4), A113112 (T^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^5)[r-1,c-1])+(M^5)[r-1,c]))); return(M[n+1,k+1])}

Formula

Let GF[T] denote the g.f. of triangular matrix T. Then GF[T] = 1 + x*(1+y)*GF[T^5] and for all integer p>=1: GF[T^p] = 1 + x*Sum_{j=1..p} GF[T^(p+4*j)] + x*y*GF[T^(5*p)].

A113077 Column 3 of square table A093729; a(n) gives the number of n-th generation descendents of a node labeled (3) in the tree of tournament sequences, for n>=0.

Original entry on oeis.org

1, 3, 15, 123, 1656, 36987, 1391106, 89574978, 10036638270, 1986129275673, 703168200003336, 450303519404234922, 526421174510139860241, 1132076561237754405471033, 4507472672071759672232970720
Offset: 0

Views

Author

Paul D. Hanna, Oct 14 2005

Keywords

Comments

Also equals column 0 of the matrix cube of triangle A097710, which satisfies the matrix recurrence: A097710(n,k) = [A097710^2](n-1,k-1) + [A097710^2](n-1,k) for n>k>=0.

Examples

			The tree of tournament sequences of descendents of a node labeled (3) begins:
[3]; generation 1: 3->[4,5,6]; generation 2: 4->[5,6,7,8],
5->[6,7,8,9,10], 6->[7,8,9,10,11,12]; ...
Then a(n) gives the number of nodes in generation n.
Also, a(n+1) = sum of labels of nodes in generation n.
		

Crossrefs

Programs

  • PARI
    {a(n,q=2)=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^q)[r-1,c-1])+(M^q)[r-1,c]))); return((M^3)[n+1,1])}

A113078 Number of tournament sequences: a(n) gives the number of n-th generation descendents of a node labeled (4) in the tree of tournament sequences.

Original entry on oeis.org

1, 4, 26, 274, 4721, 134899, 6501536, 537766009, 77598500096, 19821981700354, 9077118324755246, 7531446638893873684, 11423775838657143826346, 31914367054676982206368909, 165251261153335414813452988541
Offset: 0

Views

Author

Paul D. Hanna, Oct 14 2005

Keywords

Comments

Equals column 4 of square table A093729. Also equals column 0 of the matrix 4th power of triangle A097710, which satisfies the matrix recurrence: A097710(n,k) = [A097710^2](n-1,k-1) + [A097710^2](n-1,k) for n>k>=0.

Examples

			The tree of tournament sequences of descendents of a node labeled (4) begins:
[4]; generation 1: 4->[5,6,7,8]; generation 2: 5->[6,7,8,9,10],
6->[7,8,9,10,11,12], 7->[8,9,10,11,12,13,14],
8->[9,10,11,12,13,14,15,16]; ...
Then a(n) gives the number of nodes in generation n.
Also, a(n+1) = sum of labels of nodes in generation n.
		

Crossrefs

Programs

  • PARI
    {a(n,q=2)=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^q)[r-1,c-1])+(M^q)[r-1,c]))); return((M^4)[n+1,1])}

A113079 Number of tournament sequences: a(n) gives the number of n-th generation descendents of a node labeled (5) in the tree of tournament sequences.

Original entry on oeis.org

1, 5, 40, 515, 10810, 376175, 22099885, 2231417165, 393643922005, 123097221805100, 69087264010363930, 70321483026073531730, 130954011392485408662370, 449450774746306949114288795
Offset: 0

Views

Author

Paul D. Hanna, Oct 14 2005

Keywords

Comments

Equals column 5 of square table A093729. Also equals column 0 of the matrix 5th power of triangle A097710, which satisfies the matrix recurrence: A097710(n,k) = [A097710^2](n-1,k-1) + [A097710^2](n-1,k) for n>k>=0.

Examples

			The tree of tournament sequences of descendents of a node labeled (5) begins:
[5]; generation 1: 5->[6,7,8,9,10]; generation 2:
6->[7,8,9,10,11,12], 7->[8,9,10,11,12,13,14],
8->[9,10,11,12,13,14,15,16], 9->[10,11,12,13,14,15,16,17,18],
10->[11,12,13,14,15,16,17,18,19,20]; ...
Then a(n) gives the number of nodes in generation n.
Also, a(n+1) = sum of labels of nodes in generation n.
		

Crossrefs

Programs

  • PARI
    {a(n,q=2)=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^q)[r-1,c-1])+(M^q)[r-1,c]))); return((M^5)[n+1,1])}

A113084 Triangle T, read by rows, that satisfies the recurrence: T(n,k) = [T^3](n-1,k-1) + [T^3](n-1,k) for n>k>=0, with T(n,n)=1 for n>=0, where T^3 is the matrix third power of T.

Original entry on oeis.org

1, 1, 1, 3, 4, 1, 21, 33, 13, 1, 331, 586, 294, 40, 1, 11973, 23299, 13768, 2562, 121, 1, 1030091, 2166800, 1447573, 333070, 22569, 364, 1, 218626341, 490872957, 361327779, 97348117, 8466793, 200931, 1093, 1, 118038692523, 280082001078
Offset: 0

Views

Author

Paul D. Hanna, Oct 14 2005

Keywords

Comments

Column 0 of the matrix power p, T^p, equals the number of 3-tournament sequences having initial term p.

Examples

			Triangle T begins:
1;
1,1;
3,4,1;
21,33,13,1;
331,586,294,40,1;
11973,23299,13768,2562,121,1;
1030091,2166800,1447573,333070,22569,364,1; ...
Matrix square T^2 (A113088) begins:
1;
2,1;
10,8,1;
114,118,26,1;
2970,3668,1108,80,1;
182402,257122,96416,9964,242,1; ...
where column 0 equals A113089.
Matrix cube T^3 (A113090) begins:
1;
3,1;
21,12,1;
331,255,39,1;
11973,11326,2442,120,1;
1030091,1136709,310864,22206,363,1; ...
where adjacent sums in row n of T^3 forms row n+1 of T.
		

Crossrefs

Cf. A113081; A097710, A113095, A113106; A113085 (column 0), A113088 (T^2), A113087 (row sums).

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^3)[r-1,c-1])+(M^3)[r-1,c]))); return(M[n+1,k+1])}

Formula

Let GF[T] denote the g.f. of triangular matrix T. Then GF[T] = 1 + x*(1+y)*GF[T^3] and for all integer p>=1: GF[T^p] = 1 + x*Sum_{j=1..p} GF[T^(p+2*j)] + x*y*GF[T^(3*p)].

A113095 Triangle T, read by rows, that satisfies the recurrence: T(n,k) = [T^4](n-1,k-1) + [T^4](n-1,k) for n>k>=0, with T(n,n)=1 for n>=0, where T^4 is the matrix 4th power of T.

Original entry on oeis.org

1, 1, 1, 4, 5, 1, 46, 66, 21, 1, 1504, 2398, 978, 85, 1, 146821, 255113, 122914, 14962, 341, 1, 45236404, 84425001, 46001193, 7046354, 235122, 1365, 1, 46002427696, 91159696960, 54661544301, 9933169553, 432627794, 3738738, 5461, 1
Offset: 0

Views

Author

Paul D. Hanna, Oct 14 2005

Keywords

Comments

Column 0 of the matrix power p, T^p, equals the number of 4-tournament sequences having initial term p (see A113092 for definitions).

Examples

			Triangle T begins:
  1;
  1,1;
  4,5,1;
  46,66,21,1;
  1504,2398,978,85,1;
  146821,255113,122914,14962,341,1;
  45236404,84425001,46001193,7046354,235122,1365,1; ...
Matrix third power T^3 (A113099) begins:
  1;
  3,1;
  27,15,1;
  693,513,63,1;
  52812,47619,8289,255,1; ...
 where column 0 equals A113100.
Matrix 4th power T^4 (A113101) begins:
  1;
  4,1;
  46,20,1;
  1504,894,84,1;
  146821,108292,14622,340,1;
  45236404,39188597,6812596,233758,1364,1; ...
 where adjacent sums in row n of T^4 forms row n+1 of T.
		

Crossrefs

Cf. A097710, A113084, A113106; A113092, A113096 (column 0), A113097 (T^2), A113099 (T^3), A113101 (T^4).

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^4)[r-1,c-1])+(M^4)[r-1,c]))); return(M[n+1,k+1])}

Formula

Let GF[T] denote the g.f. of triangular matrix T. Then GF[T] = 1 + x*(1+y)*GF[T^4] and for all integer p>=1: GF[T^p] = 1 + x*Sum_{j=1..p} GF[T^(p+3*j)] + x*y*GF[T^(4*p)].

A093729 Square table T, read by antidiagonals, where T(n,k) gives the number of n-th generation descendents of a node labeled (k) in the tree of tournament sequences.

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 2, 2, 1, 0, 7, 7, 3, 1, 0, 41, 41, 15, 4, 1, 0, 397, 397, 123, 26, 5, 1, 0, 6377, 6377, 1656, 274, 40, 6, 1, 0, 171886, 171886, 36987, 4721, 515, 57, 7, 1, 0, 7892642, 7892642, 1391106, 134899, 10810, 867, 77, 8, 1, 0, 627340987, 627340987, 89574978, 6501536, 376175, 21456, 1351, 100, 9, 1
Offset: 0

Views

Author

Paul D. Hanna, Apr 14 2004; revised Oct 14 2005

Keywords

Comments

Column 1, of array T and antidiagonals, equals A008934, which is the number of tournament sequences.
A tournament sequence is an increasing sequence of positive integers (t_1,t_2,...) such that t_1 = 1 and t_{i+1} <= 2*t_i, where integer k>1.

Examples

			Array begins:
  1,      1,       1,       1,       1,      1,      1,     1,     1, ...],
  0,      1,       2,       3,       4,      5,      6,     7,     8, ...],
  0,      2,       7,      15,      26,     40,     57,    77,   100, ...],
  0,      7,      41,     123,     274,    515,    867,  1351,  1988, ...],
  0,     41,     397,    1656,    4721,  10810,  21456, 38507, 64126, ...],
  0,    397,    6377,   36987,  134899, 376175, 880032, .................],
  0,   6377,  171886, 1391106, 6501536, ...],
  0, 171886, 7892642, .....................];
Antidiagonals begin as:
  1;
  0,      1;
  0,      1,      1;
  0,      2,      2,     1;
  0,      7,      7,     3,    1;
  0,     41,     41,    15,    4,   1;
  0,    397,    397,   123,   26,   5,   1;
  0,   6377,   6377,  1656,  274,  40,   6,   1;
  0, 171886, 171886, 36987, 4721, 515,  57,   7,   1;
		

Crossrefs

Cf. A008934 (column k=1 of array and antidiagonals), A093730 (antidiagonal row sums).

Programs

  • Mathematica
    t[n_?Negative, ] = 0; t[0, ] = 1; t[n_, k_] /; k <= n := t[n, k] = t[n, k - 1] - t[n-1, k] + t[n - 1, 2 k - 1] + t[n - 1, 2 k]; t[n_, k_] := t[n, k] = Sum[(-1)^(j - 1)*Binomial[n + 1, j]*t[n, k - j], {j, 1, n + 1}]; Flatten[Table[t[i - k, k - 1], {i, 10}, {k, i}]] (* Jean-François Alcover, May 31 2011, after PARI prog. *)
  • 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))))))}
    
  • PARI
    {a(n, m) = my(A=1); for(k=1, n, A = (A - q^k * r * subst( subst(A, q, q^2), r, r^2)) / (1-q)); subst(subst(A, r, q^(m-1)), q, 1)}; /* Michael Somos, Jun 19 2017 */
    
  • SageMath
    @CachedFunction
    def T(n, k):
        if n<0: return 0
        elif n==0: return 1
        elif k==0: return 0
        elif kA093729(n,k): return T(n-k,k)
    flatten([[A093729(n,k) for k in range(n+1)] for n in range(16)]) # G. C. Greubel, Feb 22 2024

Formula

T(0, k)=1 for k>=0, T(n, 0)=0 for n>=1; else T(n, k) = T(n, k-1) - T(n-1, k) + T(n-1, 2*k-1) + T(n-1, 2*k) for k<=n; else T(n, k) = Sum_{j=1..n+1} (-1)^(j-1)*C(n+1, j)*T(n, k-j) for k>n (Cook-Kleber).
Column k of T equals column 0 of the matrix k-th power of triangle A097710, which satisfies the matrix recurrence: A097710(n, k) = [A097710^2](n-1, k-1) + [A097710^2](n-1, k) for n>k>=0.
Sum_{k=0..n} T(n-k, k) = A093730(n) (antidiagonal row sums).

A097712 Lower triangular matrix T, read by rows, such that T(n,0) = 1 and T(n,k) = T(n-1,k) + T^2(n-1,k-1) for k>0, where T^2 is the matrix square of T.

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 1, 8, 7, 1, 1, 25, 44, 15, 1, 1, 111, 346, 208, 31, 1, 1, 809, 4045, 3720, 912, 63, 1, 1, 10360, 77351, 99776, 35136, 3840, 127, 1, 1, 236952, 2535715, 4341249, 2032888, 308976, 15808, 255, 1, 1, 9708797, 145895764, 319822055, 189724354, 37329584, 2608864, 64256, 511, 1
Offset: 0

Views

Author

Paul D. Hanna, Aug 24 2004

Keywords

Comments

This triangle has the same row sums and first column terms as in rows 2^n, for n>=0, of triangle A093662.

Examples

			T(5,1) = T(4,1) + T^2(4,0) = 25 + 86 = 111.
T(5,2) = T(4,2) + T^2(4,1) = 44 + 302 = 346.
T(5,3) = T(4,3) + T^2(4,2) = 15 + 193 = 208.
Rows of T begin:
  1;
  1,      1;
  1,      3,       1;
  1,      8,       7,       1;
  1,     25,      44,      15,       1;
  1,    111,     346,     208,      31,      1;
  1,    809,    4045,    3720,     912,     63,     1;
  1,  10360,   77351,   99776,   35136,   3840,   127,   1;
  1, 236952, 2535715, 4341249, 2032888, 308976, 15808, 255, 1;
Rows of T^2 begin:
       1;
       2,       1;
       5,       6,       1;
      17,      37,      14,       1;
      86,     302,     193,      30,      1;
     698,    3699,    3512,     881,     62,     1;
    9551,   73306,   96056,   34224,   3777,   126,   1;
  226592, 2458364, 4241473, 1997752, 305136, 15681, 254, 1;
Column 0 of T^2 forms A016121.
Row sums of T^2 form the first differences of A016121.
		

Crossrefs

Cf. A016121 (row sums), A093662, A097710, A097713.

Programs

  • Mathematica
    T[n_, k_] := T[n, k] = If[n < 0 || k > n, 0, If[n == k, 1, If[k == 0, 1, T[n - 1, k] + Sum[T[n - 1, j] T[j, k - 1], {j, 0, n - 1}]]]];
    Table[T[n, k], {n, 0, 9}, {k, 0, n}] // Flatten (* Jean-François Alcover, Oct 02 2019 *)
  • PARI
    T(n,k)=if(n<0 || k>n,0,if(n==k,1,if(k==0,1, T(n-1,k)+sum(j=0,n-1,T(n-1,j)*T(j,k-1));)))
    
  • SageMath
    @CachedFunction
    def T(n,k): # T = A097712
        if k<0 or k>n: return 0
        elif k==0 or k==n: return 1
        else: return T(n-1,k) + sum(T(n-1,j)*T(j,k-1) for j in range(n))
    flatten([[T(n,k) for k in range(n+1)] for n in range(13)]) # G. C. Greubel, Feb 20 2024

Formula

T(n, k) = T(n-1, k) + Sum_{j=0..n-1} T(n-1, j)*T(j, k-1), with T(n, 0) = T(n, n) = 1.
T(n, 1) = A097713(n-1), n >= 1.
Sum_{k=0..n} T(n, k) = A016121(n) (row sums).
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