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 1-4 of 4 results.

A195663 Array read by antidiagonals: Consecutive finite permutations of positive integers in reverse colexicographic order.

Original entry on oeis.org

1, 2, 2, 3, 1, 1, 4, 3, 3, 3, 5, 4, 2, 1, 2, 6, 5, 4, 2, 3, 3, 7, 6, 5, 4, 1, 2, 1, 8, 7, 6, 5, 4, 1, 2, 2, 9, 8, 7, 6, 5, 4, 4, 1, 1, 10, 9, 8, 7, 6, 5, 3, 4, 4, 4, 11, 10, 9, 8, 7, 6, 5, 3, 2, 1, 2, 12, 11, 10, 9, 8, 7, 6, 5, 3, 2, 4, 4, 13, 12, 11, 10, 9, 8, 7, 6, 5, 3, 1, 2, 1, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 3, 1, 3, 3
Offset: 0

Views

Author

Tilman Piesk, Sep 22 2011

Keywords

Comments

Row n is the n-th finite permutation of {1,2,3,4,...}.

Examples

			The first 24 permutations of positive integers in rev colex order:
00  -->  1 2 3 4 5 6 7 8 ...
01  -->  2 1 3 4 ...
02  -->  1 3 2 4 ...
03  -->  3 1 2 4 ...
04  -->  2 3 1 4 ...
05  -->  3 2 1 4 ...
06  -->  1 2 4 3 ...
07  -->  2 1 4 3 ...
08  -->  1 4 2 3 ...
09  -->  4 1 2 3 ...
10  -->  2 4 1 3 ...
11  -->  4 2 1 3 ...
12  -->  1 3 4 2 ...
13  -->  3 1 4 2 ...
14  -->  1 4 3 2 ...
15  -->  4 1 3 2 ...
16  -->  3 4 1 2 ...
17  -->  4 3 1 2 ...
18  -->  2 3 4 1 ...
19  -->  3 2 4 1 ...
20  -->  2 4 3 1 ...
21  -->  4 2 3 1 ...
22  -->  3 4 2 1 ...
23  -->  4 3 2 1 ...
		

Crossrefs

Cf. A055089 (a very compact representation of these permutations).
Cf. A195664 (same for nonnegative integers, so all entries are smaller by 1).

Formula

a(n) = A195664(n)+1.

A181897 Triangle of refined rencontres numbers: T(n,k) is the number of permutations of n elements with cycle type k (k-th integer partition, defined by A194602).

Original entry on oeis.org

1, 1, 1, 1, 3, 2, 1, 6, 8, 3, 6, 1, 10, 20, 15, 30, 20, 24, 1, 15, 40, 45, 90, 120, 144, 15, 90, 40, 120, 1, 21, 70, 105, 210, 420, 504, 105, 630, 280, 840, 210, 504, 420, 720, 1, 28, 112, 210, 420, 1120, 1344, 420, 2520, 1120, 3360, 1680, 4032
Offset: 1

Views

Author

Tilman Piesk, Mar 31 2012

Keywords

Comments

T(n,k) tells how often k appears among the first n! entries of A198380, i.e., how many permutations of n elements have the cycle type denoted by k.
This triangle is a refinement of the rencontres numbers A008290, which tell only how many permutations of n elements actually move a certain number of elements. How many of these permutations have a certain cycle type is a more detailed question, answered by this triangle.
The rows are counted from 1, the columns from 0.
Row lengths: 1, 2, 3, 5, 7, 11, ... (partition numbers A000041).
Row sums: 1, 2, 6, 24, 120, 720, ... (factorial numbers A000142).
Row maxima: 1, 1, 3, 8, 30, 144, ... (A059171).
Distinct entries per row: 1, 1, 3, 4, 6, 7, ... (A073906).
It follows from the formula given by Carlos Mafra that the rows of the triangle correspond to the coefficients of the modified Bell polynomials. - Sela Fried, Dec 08 2021
For k>0, the k-th column of triangle T(n,k) is a scaled copy of binomial coefficients binomial(n,q) where q is the least value for which p(q) exceeds or equals k+1, with p() being the integer partitions counting function, A000041(q). E.g., for column 4, the relevant binomial coefficients have q=4 as p(4)=5; for column 5, we have q=5 as p(5)>6; for column 6, we have q=5 as p(5)=7. The scale factor for column k is given by A385081(k+1). This triangle gives coefficients for expressing the characteristic polynomial and determinant of a matrix solely in terms of traces; see extended comment, below, under "Links". - Gregory Gerard Wojnar, Jun 24 2025

Examples

			Triangle begins:
  1;
  1,  1;
  1,  3,  2;
  1,  6,  8,  3,  6;
  1, 10, 20, 15, 30,  20,  24;
  1, 15, 40, 45, 90, 120, 144, 15, 90, 40, 120;
  ...
		

Crossrefs

Cf. A036039 and references therein for different ordering of terms within each row.

Programs

  • Mathematica
    Table[CoefficientRules[ n! CycleIndex[SymmetricGroup[n], s] // Expand][[All, 2]], {n, 1, 8}] // Grid (* Geoffrey Critzer, Nov 09 2014 *)
    (* Alternative program *)
    partitionMultiplicities[aPartn_]:=Table[Count[aPartn,m],{m,Total[aPartn]}]
    partitionBase[aPartn_]:=Sum[m*aPartn[[m]],{m,Length[aPartn]}]
    partitionFactorial[aPartn_]:=Product[m^aPartn[[m]],{m,partitionBase[aPartn]}]
    partitionParts[aPartn_]:=Sum[aPartn[[m]],{m,Length[aPartn]}]
    A181897[aPartn_]:=Multinomial@@aPartn*partitionBase[aPartn]!/(partitionFactorial[aPartn]*partitionParts[aPartn]!)
    Grid[Table[Map[A181897,ReverseSort[Map[partitionMultiplicities,Partitions[n]],LexicographicOrder]],{n,2,12}]] (* Gregory Gerard Wojnar, Jun 24 2025 *)

Formula

T(n,1) = A000217(n).
T(n,2) = A007290(n).
Let m2, m3, ... count the appearances of 2, 3, ... in the cycle type. E.g., the cycle type 2, 2, 2, 3, 3, 4 implies m2=3, m3=2, m4=1. Then T(n;m2,m3,m4,...) = n!/((2^m2 3^m3 4^m4 ...) m1!m2!m3!m4! ...) where m1 = n - 2m2 - 3m3 - 4m4 - ... . - Carlos Mafra, Nov 25 2014

A055090 Number of cycles (excluding fixed points) of the n-th finite permutation in reversed colexicographic ordering (A055089).

Original entry on oeis.org

0, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 2, 2, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 2, 2, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 2, 2, 1, 1, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1, 2
Offset: 0

Views

Author

Antti Karttunen, Apr 18 2000

Keywords

Comments

Among the first n! entries k appears A136394(n,k) times. - Tilman Piesk, Apr 06 2012

Crossrefs

Cf. A195663, A195664, A055089 (ordered finite permutations).
Cf. A198380 (cycle type of the n-th finite permutation).

Programs

  • Maple
    with(group); seq(nops(convert(PermRevLexUnrank(j),'disjcyc')),j=0..)];
    # Procedure PermRevLexUnrank given in A055089.

Formula

a(n) = A055093(n) - A055091(n).
a(n) = A056170(A290095(n)) = A060128(A060126(n)). - Antti Karttunen, Dec 30 2017

Extensions

Name changed by Tilman Piesk, Apr 06 2012

A195664 Array read by antidiagonals: Consecutive finite permutations of nonnegative integers in reverse colexicographic order.

Original entry on oeis.org

0, 1, 1, 2, 0, 0, 3, 2, 2, 2, 4, 3, 1, 0, 1, 5, 4, 3, 1, 2, 2, 6, 5, 4, 3, 0, 1, 0, 7, 6, 5, 4, 3, 0, 1, 1, 8, 7, 6, 5, 4, 3, 3, 0, 0, 9, 8, 7, 6, 5, 4, 2, 3, 3, 3, 10, 9, 8, 7, 6, 5, 4, 2, 1, 0, 1, 11, 10, 9, 8, 7, 6, 5, 4, 2, 1, 3, 3, 12, 11, 10, 9, 8, 7, 6, 5, 4, 2, 0, 1, 0, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 2, 0, 2, 2
Offset: 0

Views

Author

Tilman Piesk, Sep 22 2011

Keywords

Comments

Row n is the n-th finite permutation of {0,1,2,3...}.

Examples

			The first 24 permutations of nonnegative integers in rev colex order:
00  -->  0 1 2 3 4 5 6 7 ...
01  -->  1 0 2 3 ...
02  -->  0 2 1 3 ...
03  -->  2 0 1 3 ...
04  -->  1 2 0 3 ...
05  -->  2 1 0 3 ...
06  -->  0 1 3 2 ...
07  -->  1 0 3 2 ...
08  -->  0 3 1 2 ...
09  -->  3 0 1 2 ...
10  -->  1 3 0 2 ...
11  -->  3 1 0 2 ...
12  -->  0 2 3 1 ...
13  -->  2 0 3 1 ...
14  -->  0 3 2 1 ...
15  -->  3 0 2 1 ...
16  -->  2 3 0 1 ...
17  -->  3 2 0 1 ...
18  -->  1 2 3 0 ...
19  -->  2 1 3 0 ...
20  -->  1 3 2 0 ...
21  -->  3 1 2 0 ...
22  -->  2 3 1 0 ...
23  -->  3 2 1 0 ...
		

Crossrefs

Cf. A195663 (same for positive integers, so all entries are bigger by 1).

Formula

a(n) = A195663(n)-1.
Showing 1-4 of 4 results.