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 1-6 of 6 results.

A052502 Number of permutations sigma of [3n] without fixed points such that sigma^3 = Id.

Original entry on oeis.org

1, 2, 40, 2240, 246400, 44844800, 12197785600, 4635158528000, 2345390215168000, 1524503639859200000, 1237896955565670400000, 1227993779921145036800000, 1461312598106162593792000000, 2054605512937264606871552000000
Offset: 0

Views

Author

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

Keywords

Comments

For n >= 1 a(n) is the size of the conjugacy class in the symmetric group S_(3n) consisting of permutations whose cycle decomposition is a product of n disjoint 3-cycles.

References

  • F. W. J. Olver, Asymptotics and special functions, Academic Press, 1974, pages 336-344.

Crossrefs

Cf. A000142. Row sums of triangle A060063.
First column of array A091752 (also negative of second column).
Equals row sums of A157702. - Johannes W. Meijer, Mar 07 2009
Karol A. Penson suggested that the row sums of A060063 coincide with this entry.
Trisection of column k=3 of A261430.

Programs

  • GAP
    List([0..20], n-> Factorial(3*n)/(3^n*Factorial(n))) # G. C. Greubel, May 14 2019
  • Magma
    [Factorial(3*n)/(3^n*Factorial(n)): n in [0..20]]; // G. C. Greubel, May 14 2019
    
  • Maple
    spec := [S,{S=Set(Union(Cycle(Z,card=3)))},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
  • Mathematica
    Table[(3*n)!/(3^n*n!), {n, 0, 20}] (* G. C. Greubel, May 14 2019 *)
  • PARI
    {a(n) = (3*n)!/(3^n*n!)}; \\ G. C. Greubel, May 14 2019
    
  • Sage
    [factorial(3*n)/(3^n*factorial(n)) for n in (0..20)] # G. C. Greubel, May 14 2019
    

Formula

From Ahmed Fares (ahmedfares(AT)my-deja.com), Apr 21 2001: (Start)
a(n) = (3*n)!/(3^n * n!).
a(n) ~ sqrt(3) * 9^n * (n/e)^(2n). (End)
E.g.f.: (every third coefficient of) exp(x^3/3).
G.f.: hypergeometric3F0([1/3, 2/3, 1], [], 9*x).
D-finite with recurrence a(n) = (3*n-1)*(3*n-2)*a(n-1) for n >= 1, with a(0) = 1.
Write the generating function for this sequence in the form A(x) = Sum_{n >= 0} a(n)* x^(2*n+1)/(2*n+1)!. The g.f. A(x) satisfies A'(x)*( 1 - A(x)^2) = 1. Robert Israel remarks that consequently A(x) is a root of z^3 - 3*z + 3*x with A(0) = 0. Cf. A001147, A052504 and A060706. - Peter Bala, Jan 02 2015
From Peter Bala, Feb 27 2024: (Start)
u(n) := a(n+1) satisfies the second-order recurrence u(n) = 18*n*u(n-1) + (3*n - 1)^2*(3*n - 2)^2*u(n-2) with u(0) = 2 and u(1) = 40.
A second solution to the recurrence is given by v(n) := u(n)*Sum_{k = 0..n} (-1)^k/((3*k + 1)*(3*k + 2)) with v(0) = 1 and v(1) = 18.
This leads to the continued fraction expansion (2/3)*log(2) = Sum_{k = 0..n} (-1)^k/((3*k + 1)*(3*k + 2)) = Limit_{n -> oo} v(n)/u(n) = 1/(2 + (1*2)^2/(18 + (4*5)^2/(2*18 + (7*8)^2/(3*18 + (10*11)^2/(4*18 + ... ))))). (End)
From Gabriel B. Apolinario, Jul 30 2024: (Start)
a(n) = 3 * Integral_{t=0..oo} Ai(t)*t^(3*n) dt, where Ai(t) is the Airy function.
a(n) = Integral_{t=-oo..oo} Ai(t)*t^(3*n) dt. (End)

Extensions

Edited by Wolfdieter Lang, Feb 13 2004
Title improved by Geoffrey Critzer, Aug 14 2015

A261430 Number A(n,k) of permutations p of [n] without fixed points such that p^k = Id; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 2, 3, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 9, 0, 15, 0, 0, 1, 0, 0, 2, 0, 0, 40, 0, 0, 0, 1, 0, 1, 0, 3, 24, 105, 0, 105, 0, 0, 1, 0, 0, 0, 0, 20, 0, 0, 0, 0, 0, 0, 1, 0, 1, 2, 9, 0, 175, 0, 2625, 2240, 945, 0, 0
Offset: 0

Views

Author

Alois P. Heinz, Aug 18 2015

Keywords

Examples

			Square array A(n,k) begins:
  1, 1,   1,  1,    1,  1,    1,   1,    1, ...
  0, 0,   0,  0,    0,  0,    0,   0,    0, ...
  0, 0,   1,  0,    1,  0,    1,   0,    1, ...
  0, 0,   0,  2,    0,  0,    2,   0,    0, ...
  0, 0,   3,  0,    9,  0,    3,   0,    9, ...
  0, 0,   0,  0,    0, 24,   20,   0,    0, ...
  0, 0,  15, 40,  105,  0,  175,   0,  105, ...
  0, 0,   0,  0,    0,  0,  210, 720,    0, ...
  0, 0, 105,  0, 2625,  0, 4585,   0, 7665, ...
		

Crossrefs

Main diagonal gives A261431.
Cf. A008307.

Programs

  • Maple
    with(numtheory):
    A:= proc(n, k) option remember; `if`(n<0, 0, `if`(n=0, 1,
          add(mul(n-i, i=1..j-1)*A(n-j, k), j=divisors(k) minus {1})))
        end:
    seq(seq(A(n, d-n), n=0..d), d=0..14);
  • Mathematica
    A[0, 0] = A[0, 1] = 1; A[, 0|1] = 0; A[n, k_] := A[n, k] = If[n < 0, 0, If[n == 0, 1, Sum[Product[n - i, {i, 1, j - 1}]*A[n - j, k], {j, Rest @ Divisors[k]}]]]; Table[A[n, d - n], {d, 0, 14}, {n, 0, d}] // Flatten (* Jean-François Alcover, Jan 21 2017, after Alois P. Heinz *)

Formula

E.g.f. of column k: exp(Sum_{d|k, d>1} x^d/d).

A060706 For n >= 1 a(n) is the size of the conjugacy class in the symmetric group S_(4n) consisting of permutations whose cycle decomposition is a product of n disjoint 4-cycles.

Original entry on oeis.org

1, 6, 1260, 1247400, 3405402000, 19799007228000, 210384250804728000, 3692243601622976400000, 99579809935771673508000000, 3910499136177753618659160000000, 214428309633170941925556379440000000
Offset: 0

Views

Author

Ahmed Fares (ahmedfares(AT)my-deja.com), Apr 21 2001

Keywords

Comments

a(n) is the number of ways to seat 4n bridge players at n circular tables with four players at each table. - Geoffrey Critzer, Dec 17 2011

Crossrefs

Programs

  • Maple
    for n from 0 to 20 do printf(`%d,`,(4*n)! / (n! * 4^n)) od:
  • Mathematica
    nn = 40; a = x^4/4;f[list_] := Select[list, # > 0 &];
    f[Range[0, nn]! CoefficientList[Series[Exp[a], {x, 0, nn}], x]]  (* Geoffrey Critzer, Dec 17 2011 *)
  • PARI
    { for (n=0, 100, write("b060706.txt", n, " ", (4*n)! / (n! * 4^n)); ) } \\ Harry J. Smith, Jul 09 2009

Formula

a(n) = (4n)! / (n! * 4^n). Recursion: a(0) = 1, a(1) = 6, for n >= 2 a(n) = a(n-1) * C(4n - 1, 3)* 6 = a(n-1)*(4n-1)*(4n-2)*(4n-3). Using Stirling's formula in A000142 we have a(n) ~ 2 * 64^n * (n/e)^(3n).
E.g.f.: exp(x^4/4). - Geoffrey Critzer, Dec 17 2011
Write the generating function for this sequence in the form A(x) = sum_{n>=0} a(n)* x^(3*n+1)/(3*n+1)!. Then A'(x)*( 1 - A(x)^3) = 1, consequently A(x) is a root of z^4 - 4*z + 4*x with A(0) = 0. Cf. A052502. - Peter Bala, Jan 02 2015

Extensions

More terms from James Sellers, Apr 23 2001

A261317 Number of permutations sigma of [n] without fixed points such that sigma^6 = Id.

Original entry on oeis.org

1, 0, 1, 2, 3, 20, 175, 210, 4585, 24920, 101745, 1266650, 13562395, 48588540, 1082015935, 9135376250, 63098660625, 1069777108400, 13628391601825, 88520971388850, 2134604966569075, 23945393042070500, 236084869688242575, 4893567386193135650, 72576130763294383225
Offset: 0

Views

Author

Alois P. Heinz, Aug 14 2015

Keywords

Examples

			a(4) = 3: 2143, 3412, 4321.
a(5) = 20: 21453, 21534, 23154, 24513, 25431, 31254, 34152, 34521, 35124, 35412, 41523, 43251, 43512, 45132, 45213, 51432, 53214, 53421, 54123, 54231.
		

Crossrefs

Programs

  • Maple
    a:= proc(n) option remember; `if`(n<0, 0, `if`(n=0, 1,
           add(mul(n-i, i=1..j-1)*a(n-j), j=[2, 3, 6])))
        end:
    seq(a(n), n=0..30);
  • Mathematica
    a[n_] := a[n] = If[n < 0, 0, If[n == 0, 1, Sum[Product[n - i, {i, 1, j - 1}]*a[n - j], {j, {2, 3, 6}}]]];
    Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Jun 10 2018, from Maple *)

Formula

E.g.f.: exp(x^2*(x^4+2*x+3)/6).
D-finite with recurrence a(n) +(-n+1)*a(n-2) -(n-1)*(n-2)*a(n-3) -(n-5)*(n-1)*(n-2)*(n-3)*(n-4)*a(n-6)=0. - R. J. Mathar, Jul 04 2023

A261381 Number of permutations sigma of [n] without fixed points such that sigma^10 = Id.

Original entry on oeis.org

1, 0, 1, 0, 3, 24, 15, 504, 105, 9072, 436401, 166320, 28750491, 3243240, 1307809503, 27965161224, 52309001745, 3795543015264, 2000776242465, 324424646818272, 17268536366932851, 22708075360010040, 3974396337125445231, 1436250980764880280, 548178165969608527353
Offset: 0

Views

Author

Alois P. Heinz, Aug 17 2015

Keywords

Examples

			a(4) = 3: 2143, 3412, 4321:
a(5) = 24: 23451, 23514, 24153, 24531, 25134, 25413, 31452, 31524, 34251, 34512, 35214, 35421, 41253, 41532, 43152, 43521, 45123, 45231, 51234, 51423, 53124, 53412, 54132, 54213.
a(6) = 15: 214365, 215634, 216543, 341265, 351624, 361542, 432165, 456123, 465132, 532614, 546213, 564312, 632541, 645231, 654321.
		

Crossrefs

Programs

  • Maple
    a:= proc(n) option remember; `if`(n<0, 0, `if`(n=0, 1,
           add(mul(n-i, i=1..j-1)*a(n-j), j=[2, 5, 10])))
        end:
    seq(a(n), n=0..30);

Formula

E.g.f.: exp(x^2/2+x^5/5+x^10/10).

A377597 Table read by antidiagonals: T(n,k) = (n*k)!/(n^k*k!), n >=1, k >= 0.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 3, 2, 1, 1, 15, 40, 6, 1, 1, 105, 2240, 1260, 24, 1, 1, 945, 246400, 1247400, 72576, 120, 1, 1, 10395, 44844800, 3405402000, 1743565824, 6652800, 720, 1, 1, 135135, 12197785600, 19799007228000, 162193467211776, 4940103168000, 889574400, 5040, 1
Offset: 1

Views

Author

Peter Kagey, Nov 02 2024

Keywords

Comments

This is the number of permutations in S_{k*n} that consist of k disjoint n-cycles.

Examples

			The table begins:
n\k| 0  1     2          3               4                    5
---+-----------------------------------------------------------
 1 | 1  1     1          1               1                    1
 2 | 1  1     3         15             105                  945
 3 | 1  2    40       2240          246400             44844800
 4 | 1  6  1260    1247400      3405402000       19799007228000
 5 | 1 24 72576 1743565824 162193467211776 41363226782215962624
For example T(2,5) = (2*5)!/(2^5*5!) = 10!/(32*5!) = 945.
		

Crossrefs

Cf. A001147 (row 2), A052502 (row 3), A060706 (row 4), A052504 (row 5), A110468 (col 2).
Cf. A368213.
Showing 1-6 of 6 results.