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.

A324514 Number of aperiodic permutations of {1..n}.

Original entry on oeis.org

1, 0, 3, 16, 115, 660, 5033, 39936, 362718, 3624920, 39916789, 478953648, 6227020787, 87177645996, 1307674338105, 20922779566080, 355687428095983, 6402373519409856, 121645100408831981, 2432902004460734000, 51090942171698415483, 1124000727695858073380
Offset: 1

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Author

Gus Wiseman, Mar 04 2019

Keywords

Comments

A permutation is defined to be aperiodic if every cyclic rotation of {1..n} acts on the cycle decomposition to produce a different digraph.

Examples

			The a(4) = 16 aperiodic permutations:
  (1243) (1324) (1342) (1423)
  (2134) (2314) (2413) (2431)
  (3124) (3142) (3241) (3421)
  (4132) (4213) (4231) (4312)
		

Crossrefs

Programs

  • Mathematica
    Table[Length[Select[Permutations[Range[n]],UnsameQ@@NestList[RotateRight[#/.k_Integer:>If[k==n,1,k+1]]&,#,n-1]&]],{n,6}]
  • PARI
    a(n) = sumdiv(n, d, moebius(n/d)*(n/d)^d*d!); \\ Andrew Howroyd, Aug 19 2019

Formula

a(n) = A306669(n) * n.
a(n) = Sum_{d|n} mu(n/d)*(n/d)^d*d!. - Andrew Howroyd, Aug 19 2019

Extensions

Terms a(10) and beyond from Andrew Howroyd, Aug 19 2019

A346085 Number T(n,k) of permutations of [n] such that k is the GCD of the cycle lengths; triangle T(n,k), n>=0, 0<=k<=n, read by rows.

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 4, 0, 2, 0, 15, 3, 0, 6, 0, 96, 0, 0, 0, 24, 0, 455, 105, 40, 0, 0, 120, 0, 4320, 0, 0, 0, 0, 0, 720, 0, 29295, 4725, 0, 1260, 0, 0, 0, 5040, 0, 300160, 0, 22400, 0, 0, 0, 0, 0, 40320, 0, 2663199, 530145, 0, 0, 72576, 0, 0, 0, 0, 362880
Offset: 0

Views

Author

Alois P. Heinz, Jul 04 2021

Keywords

Examples

			T(3,1) = 4: (1)(23), (13)(2), (12)(3), (1)(2)(3).
T(4,4) = 6: (1234), (1243), (1324), (1342), (1423), (1432).
Triangle T(n,k) begins:
  1;
  0,       1;
  0,       1,      1;
  0,       4,      0,     2;
  0,      15,      3,     0,    6;
  0,      96,      0,     0,    0,    24;
  0,     455,    105,    40,    0,     0, 120;
  0,    4320,      0,     0,    0,     0,   0, 720;
  0,   29295,   4725,     0, 1260,     0,   0,   0, 5040;
  0,  300160,      0, 22400,    0,     0,   0,   0,    0, 40320;
  0, 2663199, 530145,     0,    0, 72576,   0,   0,    0,     0, 362880;
  ...
		

Crossrefs

Columns k=0-1 give: A000007, A079128.
Even bisection of column k=2 gives A346086.
Row sums give A000142.
T(2n,n) gives A110468(n-1) for n >= 1.

Programs

  • Maple
    b:= proc(n, g) option remember; `if`(n=0, x^g, add((j-1)!
          *b(n-j, igcd(g, j))*binomial(n-1, j-1), j=1..n))
        end:
    T:= n-> (p-> seq(coeff(p, x, i), i=0..n))(b(n, 0)):
    seq(T(n), n=0..12);
  • Mathematica
    b[n_, g_] := b[n, g] = If[n == 0, x^g, Sum[(j - 1)!*
         b[n - j, GCD[g, j]] Binomial[n - 1, j - 1], {j, n}]];
    T[n_] := CoefficientList[b[n, 0], x];
    Table[T[n], {n, 0, 12}] // Flatten (* Jean-François Alcover, Aug 30 2021, after Alois P. Heinz *)

Formula

Sum_{k=1..n} k * T(n,k) = A346066(n).
Sum_{prime p <= n} T(n,p) = A359951(n). - Alois P. Heinz, Jan 20 2023

A226388 Number of n-permutations such that all cycle lengths have a common divisor >= 2.

Original entry on oeis.org

0, 0, 1, 2, 9, 24, 265, 720, 11025, 62720, 965601, 3628800, 130478425, 479001600, 19151042625, 191132125184, 4108830350625, 20922789888000, 1448301616386625, 6402373705728000, 466136852576275881, 5675242696048640000, 193688172394325870625, 1124000727777607680000
Offset: 0

Views

Author

Geoffrey Critzer, Jun 05 2013

Keywords

Comments

a(p) = (p-1)! for p a prime.

Examples

			a(6) = 265 counting permutations with cycle types: 6; 4-2; 3-3; 2-2-2; of which there are 120 + 90 + 40 + 15 = 265.
		

Crossrefs

Programs

  • Maple
    with(combinat):
    b:= proc(n, i, g) option remember; `if`(n=0, `if`(g>1, 1, 0),
          `if`(i<2, 0, b(n, i-1, g) +`if`(igcd(g, i)<2, 0,
           add((i-1)!^j/j! *multinomial(n, i$j, n-i*j)*
             b(n-i*j, i-1, igcd(i, g)), j=1..n/i))))
        end:
    a:= n-> b(n, n, 0):
    seq(a(n), n=0..30);  # Alois P. Heinz, Jun 06 2013
    # second Maple program:
    b:= proc(n, g) option remember; `if`(n=0, `if`(g>1, 1, 0), add(
          (j-1)!*b(n-j, igcd(g, j))*binomial(n-1, j-1), j=1..n))
        end:
    a:= n-> b(n, 0):
    seq(a(n), n=0..30);  # Alois P. Heinz, Jul 04 2021
  • Mathematica
    f[list_] :=
    Total[list]!/Apply[Times, Table[list[[i]], {i, 1, Length[list]}]]/
      Apply[Times,
       Select[Table[
          Count[list, i], {i, 1, Total[list]}], # > 0 &]!]; Table[
    Total[Map[f, Select[Partitions[n], Apply[GCD, #] > 1 &]]], {n, 0,
      25}]

Formula

a(n) = n! - A079128(n) for n >= 1. - Alois P. Heinz, Jul 04 2021

A079129 Number of degree-n permutations with pairwise coprime cycle lengths.

Original entry on oeis.org

1, 1, 2, 6, 21, 105, 530, 3710, 27265, 229705, 2083354, 24025694, 263359173, 3457302849, 44575118874, 600902614598, 9242750538593, 169974915437041, 2905860232733458, 56257078771371478, 1041600031067604437, 19990420041926339577, 419763750266646291714
Offset: 0

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Author

Keywords

Crossrefs

Extensions

More terms from Alois P. Heinz, Jan 10 2014

A359951 Number of permutations of [n] such that the GCD of the cycle lengths is a prime.

Original entry on oeis.org

0, 0, 1, 2, 3, 24, 145, 720, 4725, 22400, 602721, 3628800, 67692625, 479001600, 12924021825, 103953833984, 2116670180625, 20922789888000, 959231402754625, 6402373705728000, 257071215652932681, 3242340687872000000, 142597230222616430625, 1124000727777607680000
Offset: 0

Views

Author

Alois P. Heinz, Jan 19 2023

Keywords

Examples

			a(2) = 1: (12).
a(3) = 2: (123), (132).
a(4) = 3: (12)(34), (13)(24), (14)(23).
a(5) = 24: (12345), (12354), (12435), (12453), (12534), (12543), (13245), (13254), (13425), (13452), (13524), (13542), (14235), (14253), (14325), (14352), (14523), (14532), (15234), (15243), (15324), (15342), (15423), (15432).
		

Crossrefs

Programs

  • Maple
    b:= proc(n, g) option remember; `if`(n=0, `if`(isprime(g), 1, 0),
          add(b(n-j, igcd(j, g))*(n-1)!/(n-j)!, j=1..n))
        end:
    a:= n-> b(n, 0):
    seq(a(n), n=0..23);
  • Mathematica
    b[n_, g_] := b[n, g] = If[n == 0, If[PrimeQ[g], 1, 0], Sum[b[n - j, GCD[j, g]]*(n - 1)!/(n - j)!, {j, 1, n}]];
    a[n_] := b[n, 0];
    Table[a[n], {n, 0, 23}] (* Jean-François Alcover, Dec 13 2023, after Alois P. Heinz *)

Formula

a(n) = Sum_{prime p <= n} A346085(n,p).
a(p) = (p-1)! for prime p.

A383878 Number of permutations of [n] with distinct cycle lengths whose GCD is 1.

Original entry on oeis.org

0, 1, 0, 3, 8, 50, 264, 2394, 15840, 158976, 1490400, 20124720, 181543680, 3213905760, 36459964800, 602127540000, 9045463311360, 187660890063360, 2596164765465600, 64849189355274240, 1037566851245568000, 24684232291242854400, 498833466644833689600
Offset: 0

Views

Author

Alois P. Heinz, May 13 2025

Keywords

Examples

			a(3) = 3: (1)(23), (13)(2), (12)(3).
a(4) = 8: (1)(234), (1)(243), (134)(2), (143)(2), (124)(3), (142)(3), (123)(4), (132)(4).
		

Crossrefs

Programs

  • Maple
    b:= proc(n, i, m) option remember; `if`(i*(i+1)/2 b(n$2, 0):
    seq(a(n), n=0..23);
Showing 1-6 of 6 results.