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 61-68 of 68 results.

A349782 Triangle read by rows, T(n, k) = Sum_{j=0..k} |Stirling1(n, j)|.

Original entry on oeis.org

1, 0, 1, 0, 1, 2, 0, 2, 5, 6, 0, 6, 17, 23, 24, 0, 24, 74, 109, 119, 120, 0, 120, 394, 619, 704, 719, 720, 0, 720, 2484, 4108, 4843, 5018, 5039, 5040, 0, 5040, 18108, 31240, 38009, 39969, 40291, 40319, 40320, 0, 40320, 149904, 268028, 335312, 357761, 362297, 362843, 362879, 362880
Offset: 0

Views

Author

Peter Luschny, Dec 02 2021

Keywords

Comments

T(n, k) is the number of permutations of n objects that contain at most k cycles.

Examples

			Triangle starts:
[0] 1;
[1] 0, 1;
[2] 0, 1,    2;
[3] 0, 2,    5,     6;
[4] 0, 6,    17,    23,    24;
[5] 0, 24,   74,    109,   119,   120;
[6] 0, 120,  394,   619,   704,   719,   720;
[7] 0, 720,  2484,  4108,  4843,  5018,  5039,  5040;
[8] 0, 5040, 18108, 31240, 38009, 39969, 40291, 40319, 40320;
		

Crossrefs

Row sums: A121586, central terms: A349783.

Programs

  • Maple
    T := (n, k) -> add(abs(Stirling1(n,j)), j = 0..k):
    seq(seq(T(n, k), k = 0..n), n = 0..9);
  • Mathematica
    T[n_, k_] := Sum[Abs[StirlingS1[n, j]], {j, 0, k}]; Table[T[n, k], {n, 0, 9}, {k, 0, n}] // Flatten (* Amiram Eldar, Dec 09 2021 *)
  • PARI
    T(n, k) = sum(j=0, k, abs(stirling(n, j, 1))); \\ Michel Marcus, Dec 09 2021

Formula

T(n,k) = Sum_{j=0..k} A132393(n,j). - Alois P. Heinz, Dec 10 2021

A355266 Triangle read by rows, T(n, k) = (-1)^(n-k)*Bell(k)*Stirling1(n+1, k+1), for 0 <= k <= n.

Original entry on oeis.org

1, 1, 1, 2, 3, 2, 6, 11, 12, 5, 24, 50, 70, 50, 15, 120, 274, 450, 425, 225, 52, 720, 1764, 3248, 3675, 2625, 1092, 203, 5040, 13068, 26264, 33845, 29400, 16744, 5684, 877, 40320, 109584, 236248, 336420, 336735, 235872, 110838, 31572, 4140
Offset: 0

Views

Author

Peter Luschny and Mélika Tebni, Jul 05 2022

Keywords

Examples

			Triangle T(n, k) begins:
[0]    1;
[1]    1,      1;
[2]    2,      3,     2;
[3]    6,     11,    12,      5;
[4]   24,     50,    70,     50,    15;
[5]  120,    274,   450,    425,   225,     52;
[6]  720,   1764,  3248,   3675,  2625,   1092,  203;
[7] 5040,  13068, 26264,  33845, 29400,  16744, 5684, 877;
		

Crossrefs

Cf. A002720 (row sums), A000166 (alternating row sums), A000110 (main diagonal), A000142 (column 0).

Programs

  • Maple
    T := (n, k) -> (-1)^(n-k)*combinat:-bell(k)*Stirling1(n+1, k+1):
    seq(seq(T(n, k), k = 0..n), n = 0..8);
  • Python
    from functools import cache
    @cache
    def b(n: int, k=0):
        return int(n < 1) or k * b(n - 1, k) + b(n - 1, k + 1)
    @cache
    def s(n: int) -> list[int]:
        if n == 0: return [1]
        row = [0] + s(n - 1)
        for k in range(1, n): row[k] = row[k] + (n - 1) * row[k + 1]
        return row
    def A355266_row(n):
        return [s * b(k - 1) for k, s in enumerate(s(n + 1))][1:]
    for n in range(9): print(A355266_row(n))

Formula

T(n, k) = A000110(k) * A130534(n, k).
Sum_{k=0..n} T(n, k) = n!*Laguerre(n, -1) = A002720(n).
Sum_{k=0..n} (-1)^k*T(n, k) = !n = n!*A053557(n)/A053556(n) = A000166(n).

A371741 Triangle read by rows: g.f. (1 - t)^(-x) * (1 + t)^(3-x).

Original entry on oeis.org

1, 3, 3, 1, 1, 3, 0, 7, 1, 0, 5, 3, 0, 11, 12, 1, 0, 9, 12, 3, 0, 30, 47, 18, 1, 0, 26, 45, 22, 3, 0, 114, 215, 125, 25, 1, 0, 102, 205, 135, 35, 3, 0, 552, 1174, 855, 265, 33, 1, 0, 504, 1122, 885, 315, 51, 3, 0, 3240, 7518, 6349, 2520, 490, 42, 1, 0, 3000, 7210, 6447, 2800, 630, 70, 3
Offset: 0

Views

Author

Peter Bala, Apr 05 2024

Keywords

Examples

			Triangle begins
  n\k |  0     1     2     3     4      5
  - - - - - - - - - - - - - - - - - - - -
   0  |  1
   1  |  3
   2  |  3     1
   3  |  1     3
   4  |  0     7     1
   5  |  0     5     3
   6  |  0    11    12     1
   7  |  0     9    12     3
   8  |  0    30    47    18     1
   9  |  0    26    45    22     3
  10  |  0   114   215   125    25     1
  11  |  0   102   205   135    35     3
  ...
		

Crossrefs

Programs

  • Maple
    with(combinat):
    T := proc (n, k); if irem(n, 2) = 0 then abs(Stirling1((1/2)*n, k)) + (3*n/2)*abs(Stirling1((n-2)/2, k)) else 3*abs(Stirling1((n-1)/2, k)) + ((n-1)/2)*abs(Stirling1((n-3)/2, k)) end if; end proc:
    seq(print(seq(T(n, k), k = 0..floor(n/2))), n = 0..12);

Formula

G.f.: (1 - t)^(-x)*(1 + t)^(3-x) = Sum_{n >= 0} R(n, x)*t^n/floor(n/2)! = 1 + 3*t + (3 + x)^t^2/1! + (1 + 3*x)*t^3/1! + x*(7 + x)*t^4/2! + x*(5 + 3*x)*t^5/2! + x*(1 + x)*(11 + x)*t^6/3! + x*(1 + x)*(9 + 3*x)*t^7/3! + x*(1 + x)*(2 + x)*(15 + x)*t^8/4! + x*(1 + x)*(2 + x)*(13 + 3*x)*t^9/4! + ....
Row polynomials: R(2*n, x) = (4*n - 1 + x) * Product_{i = 0..n-2} (x + i) for n >= 1.
R(2*n+1, x) = (4*n - 3 + 3*x) * Product_{i = 0..n-2} (x + i) for n >= 1.
T(2*n, k) = |Stirling1(n, k)| + 3*n*|Stirling1(n-1, k)| = A132393(n, k) + 3*n*A132393(n-1, k).
T(2*n+1, k) = 3*|Stirling1(n, k)| + n*|Stirling1(n-1, k)| = 3*A132393(n, k) + n*A132393(n-1, k).
T(2*n, k) = (4*n - 1)*A132393(n-1, k) + A132393(n-1, k-1).
T(2*n+1, k) = (4*n - 3)*A132393(n-1, k) + 3*A132393(n-1, k-1).
n-th row sums equals 4*floor(n/2)! for n >= 2.

A376863 Triangle of generalized Stirling numbers of the lower level of the hierarchy (section m=1).

Original entry on oeis.org

1, 3, 1, 13, 7, 1, 73, 50, 12, 1, 501, 400, 125, 18, 1, 4051, 3609, 1335, 255, 25, 1, 37633, 36463, 15214, 3485, 460, 33, 1, 394353, 408694, 186949, 48769, 7805, 763, 42, 1, 4596553, 5036792, 2479602, 714364, 131299, 15708, 1190, 52, 1, 58941091, 67714809, 35419350, 11045558, 2256933, 312375, 29190, 1770, 63, 1, 824073141, 986271823, 543025851, 180766890, 40194965, 6221397, 676893, 50970, 2535, 75, 1
Offset: 0

Views

Author

Keywords

Examples

			Triangle starts:
[0]        1;
[1]        3,        1;
[2]       13,        7,        1;
[3]       73,       50,       12,       1;
[4]      501,      400,      125,      18,       1;
[5]     4051,     3609,     1335,     255,      25,       1;
[6]    37633,    36463,    15214,    3485,     460,      33,      1;
[7]   394353,   408694,   186949,   48769,    7805,     763,     42,    1;
[8]  4596553,  5036792,  2479602,  714364,  131299,   15708,   1190,   52,     1;
		

Crossrefs

A000262 (column 0), A052852 (row sums).
Triangle for m=0: A130534.

Programs

  • Maple
    T:=(m,n,k)->add(add(Stirling1(n-j,k)*binomial(n+m,i)*binomial(n,j)*binomial(j,i)*i!*m^(j-i), j=i..n),i=0..n):m:=1:seq(seq(T(m,n,k),k=0..n),n=0..10);

Formula

T(m, n, k) = Sum_{i=0..n} Sum_{j=i..n} Stirling1(n-j, k) * binomial(n+m, i) * binomial(n, j)* binomial(j, i) * i! * m^(j - i), for m = 1.

A221916 Array of products of the list entries of the combinations of n, taken in reverse standard order.

Original entry on oeis.org

1, 1, 1, 2, 2, 1, 1, 6, 6, 3, 2, 3, 2, 1, 1, 24, 24, 12, 8, 6, 12, 8, 6, 4, 3, 2, 4, 3, 2, 1, 1, 120, 120, 60, 40, 30, 24, 60, 40, 30, 24, 20, 15, 12, 10, 8, 6, 20, 15, 12, 10, 8, 6, 5, 4, 3, 2, 5, 4, 3, 2, 1, 1, 720, 720, 360, 240, 180, 144, 120, 360, 240, 180, 144, 120, 120, 90, 72, 60, 60, 48, 40, 36, 30, 24, 120, 90, 72, 60, 60, 48, 40, 36, 30, 24, 30, 24
Offset: 0

Views

Author

Wolfdieter Lang, Feb 08 2013

Keywords

Comments

The sequence of the row lengths is 2^n = A000079(n), n >= 0.
As a preliminary some notation. The list choose(n) consists of the 2^n combinations of n, written as lists. The first entry of choose(n) is the empty combination []. The other entries are ordered lexicographically within entries of the same length, called m, and m increases from 1 to n (m=0 is reserved for the empty combination). E.g., choose(3) = [[], [1], [2], [3], [1, 2], [1, 3], [2, 3], [1, 2, 3]].
The array entry a(n,k=0) := n!, n >= 0, and for k = 1, 2, ... , 2^n-1 one takes a(n,k) = n!/product(comb(n,k,l), l = 1..m(n,k)), with m(n,k) the length of the (k+1)-th entry comb(n,k) of choose(n), and comb(n,k,l) is the l-th entry of comb(n,k). E.g., comb(3,5) = [1, 3], comb(3,5,1) = 1 and comb(3,5,2) = 3, hence a(3,5) = 3!/(1*3) = 2.
This array a(n,k) is the row reversed array A(n,k) = A221914(n,k) if one adds there A(n,0) = 1 for n >= 0.
If all entries of the present array which belong to the same m= m(n,k) value are summed one obtains the unsigned Stirling1(n+1,m+1) triangle A130534(n,m) because this is sigma_{n-m}(1,2,...,n) with the (n-m)-th elementary symmetric function of 1,2, ..., n.
For row No. n the sum of entries is (n+1)! = A000142(n+1), like for the triangle A130534.

Examples

			The array a(n,k) begins:
n\k  0   1   2  3  4   5  6  7  8  9  10  11  12  13  14  15
0:   1
1:   1   1
2:   2   2   1  1
3:   6   6   3  2  3   2  1  1
4:  24  24  12  8  6  12  8  6  4  3   2   4   3   2   1   1
...
Row n=5: 120, 120, 60, 40, 30, 24, 60, 40, 30, 24, 20, 15, 12, 10, 8, 6, 20, 15, 12, 10, 8, 6, 5, 4, 3, 2, 5, 4, 3, 2, 1, 1.
Row n=6: 720, 720, 360, 240, 180, 144, 120, 360, 240, 180, 144, 120, 120, 90, 72, 60, 60, 48, 40, 36, 30, 24, 120, 90, 72, 60, 60, 48, 40, 36, 30, 24, 30, 24, 20, 18, 15, 12, 12, 10, 8, 6, 30, 24, 20, 18, 15, 12, 12, 10, 8, 6, 6, 5, 4, 3, 2, 6, 5, 4, 3, 2, 1, 1.
The combinations for row n are choose(4) = [[], [1], [2], [3], [4], [1, 2], [1, 3], [1, 4], [2, 3], [2, 4], [3, 4], [1, 2, 3], [1, 2, 4], [1, 3, 4], [2, 3, 4], [1, 2, 3, 4]]. For k=0 one takes 4! = 24. For k >= 1 one obtains 4!/1, 4!/2, 4!/3, 4!/4; 4!/(1*2), 4!/(1*3), 4!/(1*4), 4!/(2*3), 4!/(2*4), 4!/(3*4); 4!/(1*2*3),  4!/(1*2*4), 4!/(1*3*4), 4!/(2*3*4);  4!/(1*2*3*4) giving row n=4. The semicolons separate the binomial(4,m) entries with m values from 1 to 4. The example in the comment above was k=13 leading to 4!/(1*3*4) = 2 = a(4,13).
		

Crossrefs

Formula

a(n,k) := n! for k=0, and for k =1,2, ..., 2^n-1 it is n!/product(comb(n,k,l),l=1..|comb(n,k)|) with |comb(n,k)| the number of entries of comb(n,k) which is the (k+1)-th entry of the list of combinations choose(n) (starting with the empty combination for k=0), and comb(n,k,l) is the l-th entry of the list comb(n,k). See a comment above how |comb(n,k)| = m(n,k) is determined.

A323630 Expansion of e.g.f. exp(log(1 - x)^2/2)/(1 - x). This is also the transform of the involution numbers given by the signless Stirling cycle numbers.

Original entry on oeis.org

1, 1, 3, 12, 62, 390, 2884, 24472, 234086, 2490030, 29139306, 371878056, 5138306700, 76398336924, 1215973642584, 20624305367520, 371309259462972, 7071037633297116, 141997246553420052, 2998654325698019280, 66426777891686458728, 1540117294435707244488, 37296711627004301923056
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 21 2019

Keywords

Crossrefs

Programs

  • Maple
    seq(n!*coeff(series(exp(log(1-x)^2/2)/(1-x),x=0,23),x,n),n=0..22); # Paolo P. Lava, Jan 28 2019
  • Mathematica
    nmax = 22; CoefficientList[Series[Exp[Log[1 - x]^2/2]/(1 - x), {x, 0, nmax}], x] Range[0, nmax]!
    Table[Sum[Abs[StirlingS1[n, k]] HypergeometricU[-k/2, 1/2, -1/2]/(-1/2)^(k/2), {k, 0, n}], {n, 0, 22}]
  • PARI
    my(x='x + O('x^25)); Vec(serlaplace(exp(log(1 - x)^2/2)/(1 - x))) \\ Michel Marcus, Jan 24 2019

Formula

a(n) = Sum_{k=0..n} |Stirling1(n,k)|*A000085(k).
From Emanuele Munarini, Jul 09 2022: (Start)
a(n) = Sum_{k=0..n/2} |Stirling1(n+1,2*k+1)|*binomial(2*k,k)*k!/2^k.
a(n+1) = (n+1)*a(n) - Sum_{k=1..n} binomial(n,k)*(k-1)!*a(n-k). (End)

A372973 Triangle read by rows: the exponential almost-Riordan array ( 1/(1-x) | 1/(1-x), log(1/(1-x)) ).

Original entry on oeis.org

1, 1, 1, 2, 1, 1, 6, 2, 3, 1, 24, 6, 11, 6, 1, 120, 24, 50, 35, 10, 1, 720, 120, 274, 225, 85, 15, 1, 5040, 720, 1764, 1624, 735, 175, 21, 1, 40320, 5040, 13068, 13132, 6769, 1960, 322, 28, 1, 362880, 40320, 109584, 118124, 67284, 22449, 4536, 546, 36, 1
Offset: 0

Views

Author

Stefano Spezia, May 26 2024

Keywords

Examples

			The triangle begins:
    1;
    1,   1;
    2,   1,   1;
    6,   2,   3,   1;
   24,   6,  11,   6,  1;
  120,  24,  50,  35, 10,  1;
  720, 120, 274, 225, 85, 15, 1;
  ...
		

Crossrefs

Cf. A000012 (right diagonal), A000254, A000399 (k=3), A000454 (k=4), A000482 (k=5), A001233 (k=6), A001234 (k=7), A098558 (row sums), A179865 (subdiagonal), A243569 (k=8), A243570 (k=9).
Triangle A130534 with 1st column A000142.

Programs

  • Mathematica
    T[n_,0]:=n!; T[n_,k_]:=(n-1)!/(k-1)!SeriesCoefficient[1/(1-x)Log[1/(1-x)]^(k-1),{x,0,n-1}]; Table[T[n,k],{n,0,9},{k,0,n}]//Flatten

Formula

T(n,0) = n!; T(n,k) = (n-1)!/(k-1)! * [x^(n-1)] log(1/(1-x))^(k-1)/(1-x).
T(n,1) = (n-1)! for n > 0.
T(n,2) = A000254(n-1) for n > 1.

A377058 Triangle of generalized Stirling numbers of the lower level of the hierarchy (case m=2).

Original entry on oeis.org

1, 5, 1, 32, 11, 1, 248, 113, 18, 1, 2248, 1230, 263, 26, 1, 23272, 14534, 3765, 505, 35, 1, 270400, 186992, 55654, 9115, 865, 45, 1, 3479744, 2612000, 865186, 163779, 19110, 1372, 56, 1, 49079936, 39434448, 14235388, 3013164, 408569, 36288, 2058, 68, 1
Offset: 0

Views

Author

Keywords

Comments

These numbers are a subset of the generalized Stirling numbers introduced in A370518. Therefore, we assume them to be numbers of the lower level of hierarchy with respect to A370518.

Examples

			[0]           1;
[1]           5,          1;
[2]          32,         11,         1;
[3]         248,        113,        18,        1;
[4]        2248,       1230,       263,       26,       1;
[5]       23272,      14534,      3765,      505,      35,      1;
[6]      270400,     186992,     55654,     9115,     865,     45,     1;
[7]     3479744,    2612000,    865186,   163779,   19110,   1372,    56,    1;
[8]    49079936,   39434448,  14235388,  3013164,  408569,  36288,  2058,   68,    1;
		

Crossrefs

A361649 (row sums).
Triangle for m=0: A130534.
Triangle for m=1: A376863.

Programs

  • Maple
    T := (m,n,k) -> add(add(Stirling1(n-j,k)*binomial(n+m,i)*binomial(n,j)*binomial(j,i)*i!*m^(j-i), j=i..n), i=0..n): m:=2: seq(seq(T(m,n,k), k=0..n), n=0..10);

Formula

T(m, n, k) = Sum_{i=0..n} Sum_{j=i..n} Stirling1(n-j, k)*binomial(n+m, i)*binomial(n, j)* binomial(j, i)*i!*m^(j-i), for m = 2.
Previous Showing 61-68 of 68 results.