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 15 results. Next

A053482 Binomial transform of A029767.

Original entry on oeis.org

1, 4, 21, 142, 1201, 12336, 149989, 2113546, 33926337, 611660476, 12243073621, 269456124774, 6468249055921, 168191402251432, 4709596238204901, 141291441773619106, 4521383010795364609, 153727989225714801396, 5534225015581836134677
Offset: 0

Views

Author

N. J. A. Sloane, Jan 15 2000

Keywords

Comments

This is the column k=3 of an array T(n,k) = A181783(n,k) defined by T(n,0)=T(0,k)=1 and T(n,k) = n*(k-1)*T(n-1,k) +T(n,k-1), which starts
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,...
1, 1, 2, 4, 7, 11, 16, 22, 29, 37, 46,...
1, 1, 5, 21, 63, 151, 311, 575, 981,1573,2401,...
1, 1, 16, 142, 709,2521,7186,17536,38137,75889,140716,...
1, 1, 65,1201,9709,50045,193765,614629,1682465,4110913,9176689,...
Column k=2 is A000522. The e.g.f. for column k is E_k(z) = E_(k-1)(z)/[1-(k-1)] = exp(z)/prod_{j=1..k-1} (1-j*z). - Richard Choulet, Dec 17 2012

Programs

  • Mathematica
    CoefficientList[Series[E^x/(1-3*x+2*x^2), {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Oct 02 2013 *)

Formula

E.g.f.: exp(x)*(2/(1-2x)-1/(1-x))=exp(x)/(1-3x+2x^2); a(n)=sum{k=0..n, C(n,k)*k!*(2^(k+1)-1)}; a(n)=n!*sum{k=0..n, (2^(n-k+1)-1)/k!}; a(n)=int(x^n*(exp((1-x)/2)-exp(1-x)),x,1,infty); a(n)=2*A010844(n)-A000522(n); - Paul Barry, Jan 28 2008
Conjecture: a(n) -(3*n+1)*a(n-1) +(2*n+3)*(n-1)*a(n-2) -2*(n-1)*(n-2)*a(n-3)=0. - R. J. Mathar, Sep 29 2012
a(n) = 3*n*a(n-2)-2*n*(n-1)*a(n-2)+1, derived from the array defined in the comment, which proves the previous conjecture. - Richard Choulet, Dec 17 2012
a(n) ~ n! * 2^(n+1)*exp(1/2). - Vaclav Kotesovec, Oct 02 2013

A052840 a(n) = n*A029767(n-1).

Original entry on oeis.org

0, 0, 2, 9, 56, 450, 4464, 52920, 731520, 11566800, 206035200, 4083488640, 89137843200, 2124970848000, 54929029478400, 1530259226496000, 45705137084006400, 1456873475016960000, 49362677881380864000
Offset: 0

Views

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Keywords

Comments

Old name was: A simple grammar.

Programs

  • Maple
    spec := [S,{B=Sequence(Z,1 <= card),C=Cycle(B),S=Prod(Z,C)},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
    # alternative
    A052840 := proc(n)
        log((-1+x)/(-1+2*x))*x ;
        coeftayl(%,x=0,n)*n! ;
    end proc:
    seq(A052840(n),n=0..20) ; # R. J. Mathar, Jan 20 2025
  • Mathematica
    Flatten[{0, 0, Table[n!*(2^(n-1) - 1)/(n-1), {n, 2, 20}]}] (* Vaclav Kotesovec, Jun 06 2019 *)

Formula

E.g.f.: log((-1+x)/(-1+2*x))*x.
D-finite with recurrence: a(1)=0, a(2)=2, (-2*n+2*n^3-4+4*n^2)*a(n)+(-6*n-3*n^2)*a(n+1)+(n+1)*a(n+2), i.e. (-n+1)*a(n) +3*n*(n-2)*a(n-1) -2*n*(n-1)*(n-3)*a(n-2)=0
For n > 1, a(n) = n! * (2^(n-1) - 1)/(n-1). - Vaclav Kotesovec, Jun 06 2019

A053481 First differences of A029767.

Original entry on oeis.org

2, 11, 76, 654, 6816, 83880, 1193760, 19318320, 350622720, 7056927360, 156031142400, 3760042809600, 98093779660800, 2754553785984000, 82841868639129600, 2656672553703168000, 90498598469959680000, 3263440333591646208000
Offset: 0

Views

Author

N. J. A. Sloane, Jan 15 2000

Keywords

Programs

  • Mathematica
    a[n_] := (n - 1)! * (2^n - 1); Table[a[n+2] - a[n+1], {n,0,25}] (* G. C. Greubel, Jan 19 2017 *)
  • PARI
    for(n=0,25, print1(( (n+1)!*(2^(n+2) -1) - n!*(2^(n+1) -1)), ", ")) \\ G. C. Greubel, Jan 19 2017

Formula

a(n) = (n+1)!*(2^(n+2) -1) - n!*(2^(n+1) -1) for n>=0. - G. C. Greubel, Jan 19 2017

A053483 Euler transform of A029767.

Original entry on oeis.org

1, 4, 18, 114, 900, 8845, 103861, 1427122, 22486706, 399906140, 7922936720, 173013117604, 4127746294408, 106806183646594, 2978731438384738, 89065499057526433, 2842061902985159593, 96395720127638538076, 3462922846509648162418
Offset: 0

Views

Author

N. J. A. Sloane, Jan 15 2000

Keywords

Crossrefs

Cf. A107895.

Programs

  • Mathematica
    Rest[CoefficientList[Series[Product[1/(1 - x^k)^((k-1)!*(2^k-1)), {k, 1, 20}], {x, 0, 20}], x]] (* Vaclav Kotesovec, Aug 07 2015 *)

A131222 Exponential Riordan array [1, log((1-x)/(1-2x))].

Original entry on oeis.org

1, 0, 1, 0, 3, 1, 0, 14, 9, 1, 0, 90, 83, 18, 1, 0, 744, 870, 275, 30, 1, 0, 7560, 10474, 4275, 685, 45, 1, 0, 91440, 143892, 70924, 14805, 1435, 63, 1, 0, 1285200, 2233356, 1274196, 324289, 41160, 2674, 84, 1
Offset: 0

Views

Author

Paul Barry, Jun 18 2007

Keywords

Comments

This is also the matrix product of the unsigned Lah numbers and the Stirling cycle numbers. See also A079639 and A079640 for variants based on an (1,1)-offset of the number triangles. - Peter Luschny, Apr 12 2015
The Bell transform of A029767(n+1). For the definition of the Bell transform see A264428. - Peter Luschny, Jan 18 2016
Essentially the same as A079638. - Peter Bala, Feb 12 2022

Examples

			Number triangle starts:
  1,
  0,   1;
  0,   3,   1;
  0,  14,   9,   1;
  0,  90,  83,  18,  1;
  0, 744, 870, 275, 30,  1;
  ...
		

Crossrefs

Programs

  • Maple
    RioExp := (d,h,n,k) -> coeftayl(d*h^k, x=0,n)*n!/k!:
    A131222 := (n,k) -> RioExp(1,log((1-x)/(1-2*x)),n,k):
    seq(print(seq(A131222(n,k),k=0..n)),n=0..5); # Peter Luschny, Apr 15 2015
    # The function BellMatrix is defined in A264428.
    BellMatrix(n -> `if`(n=0,1,n!*(2^(n+1)-1)), 9); # Peter Luschny, Jan 27 2016
  • Mathematica
    BellMatrix[f_Function, len_] := With[{t = Array[f, len, 0]}, Table[BellY[n, k, t], {n, 0, len - 1}, {k, 0, len - 1}]];
    rows = 12;
    M = BellMatrix[If[# == 0, 1, #! (2^(#+1) - 1)]&, rows];
    Table[M[[n, k]], {n, 1, rows}, {k, 1, n}] // Flatten (* Jean-François Alcover, Jun 24 2018, after Peter Luschny *)
  • Maxima
    T(n,m):=if n=0 and m=0 then 1 else n!*sum((stirling1(k,m)*2^(n-k)*binomial(n-1,k-1))/k!,k,m,n); /* Vladimir Kruchinin, Sep 27 2012 */
    
  • Sage
    def Lah(n, k):
        if n == k: return 1
        if k<0 or  k>n: return 0
        return (k*n*gamma(n)^2)/(gamma(k+1)^2*gamma(n-k+1))
    matrix(ZZ, 8, Lah) * matrix(ZZ, 8, stirling_number1) # as a square matrix Peter Luschny, Apr 12 2015
    # alternatively:
    
  • Sage
    # uses[bell_matrix from A264428]
    bell_matrix(lambda n: A029767(n+1), 10) # Peter Luschny, Jan 18 2016

Formula

Row sums are A002866.
Second column is A029767.
T(n,m) = n! * Sum_{k=m..n} Stirling1(k,m)*2^(n-k)*binomial(n-1,k-1)/k!, n >= m >= 0. - Vladimir Kruchinin, Sep 27 2012

A360288 Number T(n,k) of permutations of [n] whose excedance set is the k-th finite subset of positive integers in standard order; triangle T(n,k), n>=0, 0<=k<=ceiling(2^(n-1))-1, read by rows.

Original entry on oeis.org

1, 1, 1, 1, 1, 3, 1, 1, 1, 7, 3, 7, 1, 3, 1, 1, 1, 15, 7, 31, 3, 17, 7, 15, 1, 7, 3, 7, 1, 3, 1, 1, 1, 31, 15, 115, 7, 69, 31, 115, 3, 37, 17, 69, 7, 37, 15, 31, 1, 15, 7, 31, 3, 17, 7, 15, 1, 7, 3, 7, 1, 3, 1, 1, 1, 63, 31, 391, 15, 245, 115, 675, 7, 145, 69
Offset: 0

Views

Author

Alois P. Heinz, Feb 01 2023

Keywords

Comments

The list of finite subsets of positive integers in standard statistical (or Yates) order begins: {}, {1}, {2}, {1,2}, {3}, {1,3}, {2,3}, {1,2,3}, ... cf. A048793, A048794.
The excedance set of permutation p of [n] is the set of indices i with p(i)>i, a subset of [n-1].
All terms are odd.

Examples

			T(5,4) = 3: there are 3 permutations of [5] with excedance set {3} (the 4th subset in standard order): 12435, 12534, 12543.
Triangle T(n,k) begins:
  1;
  1;
  1,  1;
  1,  3, 1,  1;
  1,  7, 3,  7, 1,  3, 1,  1;
  1, 15, 7, 31, 3, 17, 7, 15, 1, 7, 3, 7, 1, 3, 1, 1;
  ...
		

Crossrefs

Columns k=0-1 give: A000012, A000225(n-1) for n>=1.
Row sums give A000142.
Row lengths are A011782.
See A152884, A360289 for similar triangles.

Programs

  • Maple
    b:= proc(s, t) option remember; (m->
          `if`(m=0, x^(t/2), add(b(s minus {i}, t+
          `if`(i (p-> seq(coeff(p, x, i), i=0..degree(p)))(b({$1..n}, 0)):
    seq(T(n), n=0..7);
  • Mathematica
    b[s_, t_] := b[s, t] = Function [m, If[m == 0, x^(t/2), Sum[b[s ~Complement~ {i}, t + If[i < m, 2^i, 0]], {i, s}]]][Length[s]];
    T[n_] := CoefficientList[b[Range[n], 0], x];
    Table[T[n], {n, 0, 7}]  // Flatten (* Jean-François Alcover, Feb 13 2023, after Alois P. Heinz *)

Formula

Sum_{k=0..2^(n-1)-1} (k+1) * T(n,k) = A029767(n) for n>=1.
Sum_{k=0..2^(n-1)-1} (2^n-1-k) * T(n,k) = A355258(n+1) for n>=1.

A226968 Number of labeled octopi with n nodes such that each tentacle has an odd number of nodes.

Original entry on oeis.org

0, 1, 1, 8, 30, 264, 1920, 20880, 226800, 3064320, 43908480, 722131200, 12773376000, 249559833600, 5236924492800, 118911189196800, 2883421981440000, 74715282690048000, 2054450584682496000, 59855791774851072000, 1839882143683584000000
Offset: 0

Views

Author

Geoffrey Critzer, Sep 01 2013

Keywords

Crossrefs

Cf. A029767.

Programs

  • Mathematica
    nn=20;f[x_]:=x/(1-x^2);Range[0,nn]!CoefficientList[Series[Log[1/(1-f[x])],{x,0,nn}],x]

Formula

For n>=1; (n-1)!*( A000032(n) + (-1)^(n+1) -1 ).
E.g.f.: log(1/(1 - A(x))) where A(x) = x/(1-x^2).

A079638 Matrix product of unsigned Lah-triangle |A008297(n,k)| and unsigned Stirling1-triangle |A008275(n,k)|.

Original entry on oeis.org

1, 3, 1, 14, 9, 1, 90, 83, 18, 1, 744, 870, 275, 30, 1, 7560, 10474, 4275, 685, 45, 1, 91440, 143892, 70924, 14805, 1435, 63, 1, 1285200, 2233356, 1274196, 324289, 41160, 2674, 84, 1, 20603520, 38769840, 24870572, 7398972, 1151409, 98280, 4578
Offset: 1

Views

Author

Vladeta Jovovic, Jan 30 2003

Keywords

Comments

Matrix product of unsigned Lah-triangle |A008297(n,k)| and Stirling1-triangle A008275(n,k) is unsigned Stirling1-triangle |A008275(n,k)|.
Also the Bell transform of A029767(n+1). For the definition of the Bell transform see A264428. - Peter Luschny, Jan 26 2016
Essentially the same as A131222. - Peter Bala, Feb 12 2022

Examples

			Triangle begins
     1;
     3,     1;
    14,     9,    1;
    90,    83,   18,   1;
   744,   870,  275,  30,  1;
  7560, 10474, 4275, 685, 45, 1;
  ...
		

Crossrefs

Cf. A002866 (row sums), A029767 (first column), A131222.

Programs

  • Maple
    # The function BellMatrix is defined in A264428.
    # Adds (1, 0, 0, 0, ..) as column 0.
    BellMatrix(n -> n!*(2^(n+1)-1), 9); # Peter Luschny, Jan 26 2016
  • Mathematica
    BellMatrix[f_, len_] := With[{t = Array[f, len, 0]}, Table[BellY[n, k, t], {n, 0, len - 1}, {k, 0, len - 1}]];
    B = BellMatrix[Function[n, n! (2^(n + 1) - 1)], rows = 12];
    Table[B[[n, k]], {n, 2, rows}, {k, 2, n}] // Flatten (* Jean-François Alcover, Jun 28 2018, after Peter Luschny *)

Formula

T(n, k) = Sum_{i=k..n} |A008297(n, i)| * |A008275(i, k)|.
E.g.f.: ((1-x)/(1-2*x))^y. - Vladeta Jovovic, Nov 22 2003

A328055 Expansion of e.g.f. -log(1 - x / (1 - x)^2).

Original entry on oeis.org

0, 1, 5, 32, 270, 2904, 38400, 605520, 11113200, 232888320, 5488560000, 143704108800, 4138573824000, 130020673305600, 4425201196416000, 162194862064435200, 6369479157000960000, 266808274486161408000, 11874724379464826880000, 559591797303082672128000
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 03 2019

Keywords

Comments

a(n) is the number of ways to choose one element from each branch of labeled octopuses with n nodes (cf. A029767 and example below). - Enrique Navarrete, Oct 29 2023

Examples

			For n=2, the 3 labeled octopuses are the following, and there are 2+2+1 ways to choose one element from each branch:
O-1-2;
O-2-1;
1-O-2. - _Enrique Navarrete_, Oct 29 2023
		

Crossrefs

Cf. A001906, A004146, A005248, A005443, A029767, A052567 (exponential transform), A100404, A226968, A328054.

Programs

  • Magma
    [0] cat [Factorial(n - 1)*(Lucas(2*n)-2):n in [1..20]]; // Marius A. Burtea, Oct 03 2019
    
  • Mathematica
    nmax = 19; CoefficientList[Series[-Log[1 - x/(1 - x)^2], {x, 0, nmax}], x] Range[0, nmax]!
    Join[{0}, Table[(n - 1)! (LucasL[2 n] - 2), {n, 1, 19}]]
  • PARI
    my(x='x+O('x^20)); concat(0, Vec(serlaplace(-log(1 - x / (1 - x)^2)))) \\ Michel Marcus, Oct 03 2019

Formula

E.g.f.: log(1 + Sum_{k>=1} Fibonacci(2*k) * x^k).
a(n) = (n - 1)! * (Lucas(2*n) - 2) for n > 0.

A355257 Array read by ascending antidiagonals. A(n, k) = k! * [x^k] log((1 - x) / (1 - 2*x)) / (1 - x)^n, for 0 <= k <= n.

Original entry on oeis.org

0, 0, 1, 0, 1, 3, 0, 1, 5, 14, 0, 1, 7, 29, 90, 0, 1, 9, 50, 206, 744, 0, 1, 11, 77, 406, 1774, 7560, 0, 1, 13, 110, 714, 3804, 18204, 91440, 0, 1, 15, 149, 1154, 7374, 41028, 218868, 1285200, 0, 1, 17, 194, 1750, 13144, 85272, 506064, 3036144, 20603520
Offset: 0

Views

Author

Peter Luschny and Mélika Tebni, Jul 01 2022

Keywords

Comments

Conjecture: For p prime, A(n, p) == -1 (mod p) for n >= 0.
Conjecture: Let n >= 0, k >= 1 and k != 4. Then k divides A(n, k) if and only if k is not prime.
From Mélika Tebni, Jul 04 2022: (Start)
Conjecture: The polynomials of A355259 generate the k+1 column of this array.
Conjecture: For p prime and n even, (A(n, p) / (p - 1)) == 1 (mod p). (End)

Examples

			Table A(n, k) begins:
  [0] 0, 1,  3,  14,   90,   744,   7560,    91440,   1285200, ... A029767
  [1] 0, 1,  5,  29,  206,  1774,  18204,   218868,   3036144, ... A103213
  [2] 0, 1,  7,  50,  406,  3804,  41028,   506064,   7084656, ... A355171
  [3] 0, 1,  9,  77,  714,  7374,  85272,  1102968,  15908400, ... A355372
  [4] 0, 1, 11, 110, 1154, 13144, 164136,  2251920,  33923760, ... A355407
  [5] 0, 1, 13, 149, 1750, 21894, 295500,  4320420,  68487120, ... A355414
  [6] 0, 1, 15, 194, 2526, 34524, 502644,  7838928, 131198544, ...
  [7] 0, 1, 17, 245, 3506, 52054, 814968, 13543704, 239548176, ...
		

Crossrefs

Programs

  • Maple
    egf := n -> log((1 - x)/(1 - 2*x))/(1 - x)^n:
    ser := n -> series(egf(n), x, 22):
    row := n -> seq(k!*coeff(ser(n), x, k), k = 0..8):
    seq(print(row(n)), n = 0..8);
    # Alternative:
    A := (n, k) -> add(k!*binomial(k + n - 1, k - j - 1)/(j + 1), j = 0..k-1):
    seq(print(seq(A(n, k), k = 0..8)), n = 0..7);
  • Mathematica
    A[0, 0] = 0; A[n_, k_] := k! * Binomial[n+k-1, k - 1] * HypergeometricPFQ[{1 - k, 1, 1}, {2, n + 1}, -1];
    Table[A[n, k], {n, 0, 8}, {k, 0, 8}] // TableForm

Formula

A(n, k) = k!*Sum_{j=0..k-1} binomial(k + n - 1, k - j - 1) / (j + 1).
A(n, k) = k!*Sum_{j=1..k} binomial(n + k - j - 1, n - 1)*(2^j - 1) / j.
A(n, k) = k!*binomial(n + k - 1, k - 1)*hypergeom([1, 1, 1 - k], [2, n + 1], -1) except for A(0, 0) = 0.
Showing 1-10 of 15 results. Next