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 21-26 of 26 results.

A337994 T(n, k) = (k*(2*k+2)*(2*k+1)*(2*n-1)*binomial(2*(n-1),n-1))/(n*(n+1)*(n+2)) for n, k > 0 and T(0, 0) = 1. Triangle read by rows, for 0 <= k <= n.

Original entry on oeis.org

1, 0, 2, 0, 3, 15, 0, 6, 30, 84, 0, 14, 70, 196, 420, 0, 36, 180, 504, 1080, 1980, 0, 99, 495, 1386, 2970, 5445, 9009, 0, 286, 1430, 4004, 8580, 15730, 26026, 40040, 0, 858, 4290, 12012, 25740, 47190, 78078, 120120, 175032
Offset: 0

Views

Author

Peter Luschny, Nov 01 2020

Keywords

Comments

T(n, k) is divisible by A099398(n) for all 0 <= k <= n.

Examples

			Triangle starts:
[0] 1
[1] 0, 2
[2] 0, 3,    15
[3] 0, 6,    30,    84
[4] 0, 14,   70,    196,   420
[5] 0, 36,   180,   504,   1080,  1980
[6] 0, 99,   495,   1386,  2970,  5445,   9009
[7] 0, 286,  1430,  4004,  8580,  15730,  26026,  40040
[8] 0, 858,  4290,  12012, 25740, 47190,  78078,  120120, 175032
[9] 0, 2652, 13260, 37128, 79560, 145860, 241332, 371280, 541008, 755820
		

Crossrefs

Cf. A119578 (row sums), (-1)^n*A005430 (alternating row sums), A002740 (main diagonal), A007054 (col 1), A099398 (universal divisor), A000108 (Catalan).

Programs

  • Maple
    T := proc(n, k) if n = 0 then 1 else
    (k*(2*k+2)*(2*k+1)*(2*n-1)*binomial(2*(n-1), n-1))/(n*(n+1)*(n+2)) fi end:
    # Recursive:
    CatalanNumber := n -> binomial(2*n, n)/(n+1):
    T := proc(n, k) option remember; if k=0 then k^n elif k=n then CatalanNumber(n+1)* binomial(n+1, 2) else (4 - 10/(n + 2))*T(n-1, k) fi end:
    seq(seq(T(n, k), k=0..n), n=0..9);
  • Mathematica
    T[n_, k_] := If[n == 0, 1, (k (2k + 2)(2k + 1)(2n - 1) CatalanNumber[n-1])/((n + 1) (n + 2))]; Table[T[n, k], {n, 0, 9}, {k, 0, n}] // Flatten

Formula

Let t(n) denote the triangular numbers and C(n) the Catalan numbers.
T(n, k) = k*(2*n - 1)*(t(2*k + 1)/t(n + 1))*C(n - 1) for n, k > 0.
T(n, k) = k^n if k = 0; if k = n then C(n+1)*t(n+1); else T(n-1, k)*(4-10/(n+2)).

A376161 Number of support Tau-tilting modules for some algebras.

Original entry on oeis.org

3, 5, 12, 33, 98, 306, 990, 3289, 11154, 38454, 134368, 474810, 1693812, 6091780, 22064130, 80410185, 294647250, 1084922190, 4012165080, 14895504030, 55496654460, 207431394300, 777601790940, 2922867908298, 11013796950228, 41596652545756, 157434454904160, 597029454416724, 2268232385053096
Offset: 0

Views

Author

F. Chapoton, Sep 13 2024

Keywords

Comments

See Prop. A.6 in Wang's reference for the table counting Tau-tilting modules for the linear quiver modulo the relation alpha*beta = 0.

Crossrefs

Programs

  • Maple
    a := n -> -(3*n + 2)*(-4)^(n + 1)*binomial(3/2, n + 2):
    seq(a(n), n = 0..28)  # Peter Luschny, Sep 13 2024
  • Mathematica
    A376161[n_] := CatalanNumber[n]*(9*n + 6)/(n + 2);
    Array[A376161, 30, 0] (* Paolo Xausa, Sep 14 2024 *)
  • Sage
    def a(n):
        return 3*(3*n+2)*binomial(2*n+4,n+2)/4/(2*n+1)/(2*n+3)

Formula

a(n) = 3*(3*n+2)*binomial(2*n+4,n+2)/(4*(2*n+1)*(2*n+3)).
a(n) = A329533(n)/(n + 1).
From Peter Luschny, Sep 13 2024: (Start)
a(n) = (3*n + 2) * [x^n] ((1 - 4*x)^(3/2) + 12*x - 2)/(4*x^2).
a(n) = A016789(n)*(3/2)*(2*n)! * [x^(2*n)] hypergeom([], [3], x^2).
a(n) = CatalanNumber(n)*(9*n + 6)/(n + 2).
a(n) = -(3*n + 2)*(-4)^(n + 1)*binomial(3/2, n + 2).
a(n) = 2^n*(9*n + 6)*(2*n - 1)!! / (n + 2)!.
a(n) = A007054(n) * (3*n + 2) / 2.
a(n) = 6*A023999(n + 1)/(n + 2)!. (End)

A383776 a(n) = (11*n + 3 + 6/(n+2)) * Catalan(n).

Original entry on oeis.org

6, 16, 53, 186, 672, 2472, 9207, 34606, 130988, 498576, 1906346, 7316596, 28170768, 108760560, 420889995, 1632155670, 6340808820, 24673450560, 96148670310, 375164728620, 1465589068320, 5731488987120, 22436098732710, 87905595401676, 344702077523352, 1352701532137312, 5312100899224532, 20874451526714856
Offset: 0

Views

Author

F. Chapoton, May 09 2025

Keywords

Comments

It appears that for n >= 2 a(n-2) is the number of lattice points in the n-dimensional lattice polytope defined, in the space with coordinates (x_1,x_2,...,x_n), by the equations x_i >= 0 for every i, sum_i x_i <= n and x_1 + x_2 <= 2. For n=2, this is a triangle with 6 lattice points.

Crossrefs

Programs

  • Mathematica
    A383776[n_] := (11*n + 3 + 6/(n + 2))*CatalanNumber[n];
    Array[A383776, 30, 0] (* Paolo Xausa, May 15 2025 *)
  • Sage
    [(11*n+3+6/(n+2))*catalan_number(n) for n in range(12)]

Formula

a(n) = (11*n + 3 + 6/(n + 2))*Catalan(n).
G.f.: 2*(7 + 5*sqrt(1 - 4*x) - 6*x)/((1 + sqrt(1 - 4*x))^2*sqrt(1 - 4*x)). - Stefano Spezia, May 15 2025

A182534 Array read by antidiagonals: coefficient of the Euler-Mascheroni constant in below expression.

Original entry on oeis.org

1, 1, 2, 2, 2, 3, 5, 4, 2, 6, 14, 10, 3, 4, 10, 42, 28, 6, 6, 5, 20, 132, 84, 14, 12, 6, 10, 35, 429, 264, 36, 28, 10, 12, 14, 70, 1430, 858, 99, 72, 20, 20, 14, 28, 126, 4862, 2860, 286, 198, 45, 40, 20, 28, 42, 252
Offset: 1

Views

Author

John M. Campbell, May 05 2012

Keywords

Comments

The (i,j)-entry of the array is the coefficient of the Euler-Mascheroni constant in: -2^(i+2j-1)/Pi*int(log(x)*cos(x)^i*sin(x)^(2j-1)/x, x=0..infinity); see Mathematica code below.
First row: A000108.
Second row: -A002420.
Third row: A007054.
Fourth row: A002421.
Fifth row: A007272.
Sixth row: -A002422.
Eighth row: A002423.
First column: A001405.
Second column: A089408.
Odd entries on main diagonal: A126596.

Examples

			Evaluate: -256/Pi*int(cos(x)^3*log(x)*sin(x)^5/x, x=0..infinity) = 3*eulergamma-log(9/8). Thus the (3,3) entry of the array is 3, the coefficient of the Euler-Mascheroni constant in this expression.
The array begins as:
| 1   1   2   5   14  42  132 429  ... |
| 2   2   4   10  28  84  264 858  ... |
| 3   2   3   6   14  36  99  286  ... |
| 6   4   6   12  28  72  198 572  ... |
| 10  5   6   10  20  45  110 286  ... |
| 20  10  12  20  40  90  220 572  ... |
| 35  14  14  20  35  70  154 364  ... |
| 70  28  28  40  70  140 308 728  ... |
| ... ... ... ... ... ... ... ...  ... |
		

Crossrefs

Programs

  • Mathematica
    A[a_, b_] :=
      A[a, b] =
       Array[Coefficient[
          Integrate[
            Log[x]*Cos[x]^#1*Sin[x]^(2 #2 - 1)/x, {x, 0,
             Infinity}] (2^(#1 + 2 #2 - 1))/(-\[Pi]), EulerGamma] &, {a, b}];
    A[11, 11];
    Print[A[11, 11] // MatrixForm];
    Table2 = {};
    k = 1;
    While[k < 11, Table1 = {};
      i = 1;
      j = k;
      While[0 < j,
        AppendTo[Table1,
        First[Take[First[Take[A[11, 11], {i, i}]], {j, j}]]];
        j = j - 1;
        i = i + 1];
        AppendTo[Table2, Table1];
        k++];
    Print[Flatten[Table2]]

A337841 Triangle read by rows, T(n, k) = binomial(2*n-1, 2*k-1) * binomial(2*n-2*k, n-k) * (k+1) / binomial(n+k+1, n-k) for 0 <= k <= n.

Original entry on oeis.org

1, 0, 2, 0, 3, 3, 0, 6, 10, 4, 0, 14, 30, 21, 5, 0, 36, 90, 84, 36, 6, 0, 99, 275, 308, 180, 55, 7, 0, 286, 858, 1092, 780, 330, 78, 8, 0, 858, 2730, 3822, 3150, 1650, 546, 105, 9, 0, 2652, 8840, 13328, 12240, 7480, 3094, 840, 136, 10, 0, 8398, 29070, 46512, 46512, 31977, 15561, 5320, 1224, 171, 11
Offset: 0

Views

Author

Werner Schulte, Oct 30 2020

Keywords

Examples

			The triangle T(n,k) for 0 <= k <= n starts:
  n\k:  0     1      2      3      4      5      6     7     8    9  10
=======================================================================
   0 :  1
   1 :  0     2
   2 :  0     3      3
   3 :  0     6     10      4
   4 :  0    14     30     21      5
   5 :  0    36     90     84     36      6
   6 :  0    99    275    308    180     55      7
   7 :  0   286    858   1092    780    330     78     8
   8 :  0   858   2730   3822   3150   1650    546   105     9
   9 :  0  2652   8840  13328  12240   7480   3094   840   136   10
  10 :  0  8398  29070  46512  46512  31977  15561  5320  1224  171  11
etc.
		

Crossrefs

Cf. Row sums: A000984, main diagonal: A000027, 1st subdiagonal: A014105, 2nd subdiagonal: A055112, column 0: A000007, column 1: A007054.

Programs

  • Maple
    T := proc(n, k) option remember; if k = n then n+1 else
    T(n-1, k)*(2*n-2)*(2*n-1)/((n-1)*(n+2)-(k-1)*(k+2)) fi end:
    for n from 0 to 9 do seq(T(n, k), k=0..n) od; # Peter Luschny, Nov 02 2020

Formula

T(n,k) = binomial(2*n-1,n-k) * k * (2*k+1) * (2*k+2) / ((n+k)*(n+k+1)) for 1 <= k <= n, and T(n,0) = 0^n for n >= 0.
T(n,n) = n+1 for n >= 0; T(n,n-1) = (n-1) * (2*n-1) for n > 0; T(n,n-2) = (n-1) * (n-2) * (2*n-3) for n > 1.
T(n,k) = T(n-1,k) * (2*n-2) * (2*n-1) / ((n-1) * (n+2) - (k-1) * (k+2)) for 0 <= k < n with initial values T(n,n) = n+1 for n >= 0.
Row sums are A000984(n) for n >= 0.
Alternating row sums are 0 for n > 1.
Sum_{k=0..n} (-1)^k * T(n,k) * (k*(k+1)/2)^m = 0 for 0 <= m <= n-2.
T(n,1) = 12 * binomial(2*n-1,n-1)/((n+1)*(n+2)) = A007054(n) for n > 0.
T(n,k) = T(n,1)*(k*(k+1)*(2*k+1)/6)*binomial(n-1,k-1)/binomial(n+1+k,k-1) for 1 <= k <= n.
From Werner Schulte, Nov 09 2020: (Start)
T(n,k) = A128899(n,k) * (k+1) * (2*k+1) / (n+k+1) for 0 <= k <= n.
T(n,0) + Sum_{k=1..n} T(n,k) / (k*(k+1)) = A000108(n) for n >= 0. (End)

A372949 a(n) = 2*f(2*n)/(f(n)*f(n+2)) where f = A003266.

Original entry on oeis.org

1, 2, 8, 91, 2618, 199716, 39690618, 20689636692, 28215085220016, 100763710906257557, 942012688139052139766, 23056957423045790791793932, 1477460537993359748548214768630, 247860656992078740305125996374953260, 108861324945456389643061592667638024842480
Offset: 1

Views

Author

Kendra Killpatrick, May 17 2024

Keywords

Comments

Fibonacci analog of the super ballot numbers.
a(n) is also the generalized FiboCatalan number for r=1. Proof that the formula always gives a positive integer can be found in a recent paper of K. Killpatrick. The sequence is the Fibonacci analog of the super ballot numbers given by Gessel (A007054). The sequence is also the Fibonacci analog of the generalized Catalan numbers, J_r*(2n)!/(n!*(n+r+1)!) where J_r=(2r+1)!/r!, for r=1. Gessel defined the generalized Catalan numbers and proved they are integers.

Examples

			a(5) = 2*f(10)/(f(5)*f(7)) = 2*122522400/(30*3120) = 2618, where f=A003266.
		

Crossrefs

Programs

  • Mathematica
    a[n_]:=2Fibonorial[2n]/(Fibonorial[n]Fibonorial[n+2]); Array[a,15] (* Stefano Spezia, May 23 2024 *)

Formula

a(n) ~ 10 * phi^((n-3)*(n+1)) / A062073, where phi = A001622 is the golden ratio. - Vaclav Kotesovec, May 29 2024
Previous Showing 21-26 of 26 results.