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 31-35 of 35 results.

A243661 Triangle read by rows: the x = 1+q Narayana triangle at m=3.

Original entry on oeis.org

1, 4, 3, 22, 33, 12, 140, 315, 231, 55, 969, 2907, 3213, 1547, 273, 7084, 26565, 39270, 28560, 10200, 1428, 53820, 242190, 448500, 437000, 235980, 66861, 7752, 420732, 2208843, 4916457, 6009003, 4351347, 1864863, 437437, 43263, 3362260, 20173560, 52451256, 77134200, 70122000, 40320150, 14307150, 2861430, 246675
Offset: 1

Views

Author

N. J. A. Sloane, Jun 13 2014

Keywords

Comments

See Novelli-Thibon (2014) for precise definition.

Examples

			Triangle begins:
     1;
     4,     3;
    22,    33,    12;
   140,   315,   231,    55;
   969,  2907,  3213,  1547,   273;
  7084, 26565, 39270, 28560, 10200,  1428;
  ...
		

Crossrefs

The left column is A002293, the main diagonal is A001764.
The case m=1 is A126216 or A033282 (its mirror image).
The case m=2 is A243660.

Programs

  • Mathematica
    polrecip[P_, x_] := P /. x -> 1/x // Together // Numerator;
    P[n_, m_] := Sum[Binomial[m n + 1, k] Binomial[(m + 1) n - k, n - k] (1 - x)^k x^(n - k), {k, 0, n}]/(m n + 1);
    T[m_] := Reap[For[i=1, i <= 20, i++, z = polrecip[P[i, m], x] /. x -> 1+q; Sow[CoefficientList[z, q]]]][[2, 1]];
    T[3] // Flatten (* Jean-François Alcover, Oct 08 2018, from PARI *)
  • PARI
    N(n,m)=sum(k=0,n,binomial(m*n+1,k)*binomial((m+1)*n-k,n-k)*(1-x)^k*x^(n-k))/(m*n+1);
    T(m)=for(i=1,20,z=subst(polrecip(N(i,m)),x,1+q);print(Vecrev(z)));
    T(3) /* Lars Blomberg, Jul 17 2017 */

Formula

From Werner Schulte, Nov 23 2018: (Start)
T(n,k) = binomial(4*n+1-k,n-k) * binomial(3*n,k-1) / n.
More generally: T_m(n,k) = binomial((m+1)*n+1-k,n-k) * binomial(m*n,k-1) / n where m = 3.
Sum_{k=1..n} (-1)^k * T(n,k) = -1. (End)
Sum_{k = 1..n} (-1)^(k+1)*T(n,k)*binomial(x + 4*n - k + 1, 4*n - k + 1) = (x + 1) * ( Product_{k = 2..n} (x + k)^2 ) * ( Product_{k = 1..2*n+1} (x + n + k) ) / (n!*(3*n + 1)!) for n >= 1. Cf. A126216 and A243660. - Peter Bala, Oct 08 2022

Extensions

a(22)-a(39) from Lars Blomberg, Jul 12 2017

A079508 Triangle T(n,k) (n >= 2, k >= 1) of Raney numbers read by rows.

Original entry on oeis.org

1, 0, 1, 0, 2, 1, 0, 0, 5, 1, 0, 0, 5, 9, 1, 0, 0, 0, 21, 14, 1, 0, 0, 0, 14, 56, 20, 1, 0, 0, 0, 0, 84, 120, 27, 1, 0, 0, 0, 0, 42, 300, 225, 35, 1, 0, 0, 0, 0, 0, 330, 825, 385, 44, 1, 0, 0, 0, 0, 0, 132, 1485, 1925, 616, 54, 1, 0, 0, 0, 0, 0, 0, 1287, 5005, 4004, 936, 65, 1
Offset: 2

Views

Author

N. J. A. Sloane, Jan 21 2003

Keywords

Comments

There are only m nonzero entries in the m-th column.
Related to A033282: shift row n of A033282 triangle n places to the right and transpose the resulting table. - Michel Marcus, Feb 04 2014

Examples

			From _Michel Marcus_, Feb 04 2014: (Start)
Triangle starts:
  1;
  0, 1;
  0, 2, 1;
  0, 0, 5,  1;
  0, 0, 5,  9,  1;
  0, 0, 0, 21, 14,   1;
  0, 0, 0, 14, 56,  20,    1;
  0, 0, 0,  0, 84, 120,   27,    1;
  0, 0, 0,  0, 42, 300,  225,   35,   1;
  0, 0, 0,  0,  0, 330,  825,  385,  44,  1;
  0, 0, 0,  0,  0, 132, 1485, 1925, 616, 54, 1;
  ... (End)
		

Crossrefs

Row sums give A005043.
Column sums give A001003.
Alternating sum of each column is 1.
Second diagonal on right gives A000096.
Central terms give A000108.
Cf. A033282, A126216 (transposed variants).

Programs

  • GAP
    Flat(List([1..10], n->List([1..n-1], k-> Binomial(k,n-k)*Binomial(n ,k+1)/k ))); # G. C. Greubel, Jan 17 2019
  • Magma
    [[Binomial(k,n-k)*Binomial(n,k+1)/k: k in [1..n-1]]: n in [2..10]]; // G. C. Greubel, Jan 17 2019
    
  • Mathematica
    Table[Binomial[k, n-k]*Binomial[n, k+1]/k, {n,2,10}, {k,1,n-1}]//Flatten (* G. C. Greubel, Jan 17 2019 *)
  • PARI
    tabl(nn) = {for (n = 2, nn, for (k = 1, n-1, print1(binomial(k, n-k)*binomial(n, k+1)/k, ", ");); print(););} \\ Michel Marcus, Feb 04 2014
    
  • Sage
    [[binomial(k,n-k)*binomial(n,k+1)/k for k in (1..n-1)] for n in (2..10)] # G. C. Greubel, Jan 17 2019
    

Formula

T(n,k) = binomial(k, n-k) * binomial(n, k+1)/k. - Michel Marcus, Feb 04 2014
From Andrew Howroyd, Jan 24 2025: (Start)
T(n,k) = A033282(k + 2, n - k - 1) = A126216(k, 2*k - n).
G.f.: -1 + ((1 + y*x) - sqrt(1 - 2*y*x + (y^2 - 4*y)*x^2))/(2*x*y*(1 + x)).
G.f.: -1 + (1/(x*y))*Series_Reversion(x*(1 - x)/(y - y*x + x^2)). (End)

Extensions

Corrected and extended by Michel Marcus, Feb 04 2014

A183759 Unlabeled super-Catalan numbers: patterns of nonintersecting chords joining unlabeled points on a circle, triangle decomposed by number of chords.

Original entry on oeis.org

1, 1, 1, 1, 2, 3, 1, 2, 7, 7, 1, 3, 15, 33, 22, 1, 3, 24, 94, 136, 66, 1, 4, 41, 218, 525, 552, 217, 1, 4, 57, 440, 1517, 2673, 2233, 715, 1, 5, 86, 804, 3748, 9439, 12917, 8807, 2438
Offset: 1

Views

Author

David Scambler, Jan 06 2011

Keywords

Comments

Decomposition of A183757 by number of chords (pairs of parentheses). Row sums are A183757. See A183757 for description.
Triangle is
1
1 1
1 2 3
1 2 7 7
1 3 15 33 22
1 3 24 94 136 66
...
Right diagonal is apparently A007595.

Crossrefs

Decomposition of A183757.
Cf. analogous decomposition of super-Catalan numbers in triangle A033282.

A183760 Unlabeled super-Catalan numbers: patterns of nonintersecting chords joining unlabeled points on a flippable circle, triangle decomposed by number of chords.

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 1, 2, 5, 4, 1, 3, 10, 18, 12, 1, 3, 16, 51, 71, 34, 1, 4, 26, 116, 271, 280, 111, 1, 4, 36, 233, 776, 1349, 1124, 360, 1, 5, 53, 421, 1908, 4749, 6487, 4415, 1226
Offset: 1

Views

Author

David Scambler, Jan 06 2011

Keywords

Comments

Decomposition of A183758 by number of chords (pairs of parentheses). Row sums are A183758. See A183758 for description.
Triangle is
1
1 1
1 2 2
1 2 5 4
1 3 10 18 12
1 3 16 51 71 34
...
Right diagonal is apparently A001895.

Crossrefs

Decomposition of A183758. Cf. analogous decomposition of super-Catalan numbers in triangle A033282.

A357613 Triangle read by rows T(n, k) = binomial(2*n, k) * binomial(3*n - k, 2*n).

Original entry on oeis.org

1, 3, 2, 15, 20, 6, 84, 168, 105, 20, 495, 1320, 1260, 504, 70, 3003, 10010, 12870, 7920, 2310, 252, 18564, 74256, 120120, 100100, 45045, 10296, 924, 116280, 542640, 1058148, 1113840, 680680, 240240, 45045, 3432
Offset: 0

Views

Author

F. Chapoton, Oct 06 2022

Keywords

Comments

Each line should be the f-vector of a cellular complex. The sequence seems to give the coefficients in a binomial basis of the integer-valued polynomials (x+1)*(x+2)*...*(x+2*n)*(x+1)*(x+2)*...*(x+n)/(n!*(2n)!).
The precise expansion is (x+1)*(x+2)*...*(x+2*n)*(x+1)*(x+2)*...*(x+n)/(n!*(2*n)!) = Sum_{k = 0..n} (-1)^k*T(n,k)*binomial(x+3*n-k, 3*n-k), as can be verified using the WZ algorithm. For example, n = 3 gives (x+1)^2*(x+2)^2*(x+3)^2*(x+4)*(x+5)*(x+6)/(3!*6!) = 84*binomial(x+9, 9) - 168*binomial(x+8, 8) + 105*binomial(x+7, 7) - 20*binomial(x+6, 6). - Peter Bala, Jun 25 2023

Examples

			As a triangle of numbers, this starts with
  1;
  3, 2;
  15, 20, 6;
  84, 168, 105, 20;
  495, 1320, 1260, 504, 70.
Here is an example for n=1 as coefficients (up to sign) in the binomial basis of integer-valued polynomials:
(x+1)*(x+2)*(x+1)/2 = 3*binomial(x+3,3)-2*binomial(x+2,2).
		

Crossrefs

Row sums A026000. Cf. A000984, A005809 (k=0), A144485 (k=1), A033282, A110608, A243660.

Programs

  • Maple
    A357613 := proc(n,k)
        binomial(2*n,k)*binomial(3*n-k,2*n) ;
    end proc:
    seq(seq(A357613(n,k),k=0..n),n=0..10) ; # R. J. Mathar, Jul 06 2023
  • Mathematica
    Table[Binomial[2n,k]Binomial[3n-k,2n],{n,0,10},{k,0,n}]//Flatten (* Harvey P. Dale, Oct 11 2023 *)
  • SageMath
    def a(n):
        return [binomial(2 * n, k) * binomial(3 * n - k, 2 * n)
                for k in range(n + 1)]

Formula

T(n,k) = binomial(2*n, k) * binomial(3*n - k, 2*n) for 0 <= k <= n
Previous Showing 31-35 of 35 results.