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.

User: María Merino

María Merino's wiki page.

María Merino has authored 41 sequences. Here are the ten most recent ones:

A307429 Triangle read by rows: T(n,k) is the number of permutations of {1..n} at Kendall tau distance k of permutation sigma1 and k+1 Kendall tau distance of permutation sigma2, where sigma1 and sigma2 are at Kendall tau distance 1.

Original entry on oeis.org

1, 1, 0, 1, 1, 1, 0, 1, 2, 3, 3, 2, 1, 0, 1, 3, 6, 9, 11, 11, 9, 6, 3, 1, 0, 1, 4, 10, 19, 30, 41, 49, 52, 49, 41, 30, 19, 10, 4, 1, 0, 1, 5, 15, 34, 64, 105, 154, 205, 250, 281, 292, 281, 250, 205, 154, 105, 64, 34, 15, 5, 1, 0
Offset: 1

Author

Imanol Unanue, María Merino, Jose A. Lozano, Apr 08 2019

Keywords

Comments

The length of the n-th row is n(n-1)/2 + 1, where n(n-1)/2 is the maximum Kendall tau distance distance for permutations of {1..n}.

Examples

			Triangle begins:
  1;
  1, 0;
  1, 1,  1,  0;
  1, 2,  3,  3,  2,  1,  0;
  1, 3,  6,  9, 11, 11,  9,  6,  3,  1, 0;
  1, 4, 10, 19, 30, 41, 49, 52, 49, 41, 30, 19, 10, 4, 1, 0;
		

Crossrefs

Row sums give A001710.
Cf. A008302.

Programs

  • Mathematica
    T[n_] := Module[{polcoef, svalues = {}, si, j, k, c}, polcoef = CoefficientList[Series[QFactorial[n, c], {c, 0, n (n - 1)/2}], c]; For[j = 1, j <= Length[polcoef], j++, si = 0; For[k = 1, k <= j, k++, si = si + polcoef[[k]]*(-1)^(j - k)]; AppendTo[svalues, si]]; Return[svalues]]; Catenate[Table[T[n], {n, 1, 7}]]
  • PARI
    S(n, k) = my(A=1+x); for(i=1, n, A = 1 + intformal(A - q*subst(A, x, q*x +x^2*O(x^n)))/(1-q)); polcoeff(n!*polcoeff(A, n, x), k, q); \\ A008302
    T(n, k) = sum(i=0, k, (-1)^(k-i)*S(n,i));
    tabf(nn) = for (n=1, nn, for (k=0, n*(n-1)/2, print1(T(n, k), ", ")); print); \\ Michel Marcus, Apr 10 2019
    
  • SageMath
    from sage.combinat.q_analogues import q_factorial
    def A307429_row(n):
        qf = q_factorial(n).list()
        return [sum((-1)^(k-j)*qf[j] for j in range(k+1)) for k in range(n*(n-1)//2 + 1)]
    for n in range(1, 7): print(A307429_row(n)) # Peter Luschny, Sep 01 2022

Formula

T(n,k) = Sum_{j=0..k} (-1)^j * S(n,k-j), where S(n,k) = A008302(n,k) is the number of permutations of {1..n} with k inversions.

A287384 Triangle read by rows: T(n,m) is the number of inequivalent n X m matrices under action of the Klein group, with one-tenth each of 1's, 2's, 3's, 4's, 5's, 6's, 7's, 8's, 9's and 0's (ordered occurrences rounded up/down if n*m != 0 mod 10).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 29937600, 81729648000, 1, 1, 907200, 10216209600, 593970221376000, 15584018578345728000, 1, 1, 29937600, 6252318979200, 1870082229375360000, 1096699334071461120000000, 375493744214599112902800000000
Offset: 0

Author

María Merino and Imanol Unanue, May 24 2017

Keywords

Comments

Computed using Polya's enumeration theorem for coloring.

Examples

			For n = 4 and m = 3 the T(4,3)=29937600 solutions are colorings of 4 X 3 matrices in 10 colors inequivalent under the action of the Klein group with exactly 2, 2, 1, 1, 1, 1, 1, 1, 1, 1 occurrences of each color (coefficient of x1^2 x2^2 x3^1 x4^1 x5^1 x6^1 x7^1 x8^1 x9^1 x10^1).
Triangle begins:
  ==========================================
  n\m | 0  1  2   3           4
  ----|-------------------------------------
  0   | 1
  1   | 1  1
  2   | 1  1  1
  3   | 1  1  1   1
  4   | 1  1  1   29937600    81729648000
		

Formula

G.f.: g(x1,x2,x3,x4,x5,x6,x7,x8,x9,x10)=(y1^(m*n) + 3*y2^(m*n/2))/4 for even n and m; (y1^(m*n) + y1^n*y2^((m*n-m)/2) + 2*y2^(m*n/2))/4 for odd n and even m; (y1^(m*n) + y1^m*y2^((m*n-n)/2) + 2*y2^(m*n/2))/4 for even n and odd m; (y1^(m*n) + y1^n*y2^((m*n-n)/2) + y1^m*y2^((m*n-m)/2) + y1*y2^((m*n-1)/2))/4 for odd n and m; where coefficient correspond to y1=Sum_{i=1..10} x_i, y2=Sum_{i=1..10} x_i^2, and occurrences of numbers are ceiling(m*n/10) for the first k numbers and floor(m*n/10) for the last (10-k) numbers, if m*n = k mod 10.

Extensions

More terms from María Merino, Aug 01 2017

A287383 Triangle read by rows: T(n,m) is the number of inequivalent n X m matrices under action of the Klein group, with one-ninth each of 1's, 2's, 3's, 4's, 5's, 6's, 7's, 8's and 9's (ordered occurrences rounded up/down if n*m != 0 mod 9).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 90720, 1, 1, 1, 14968800, 40864824000, 1, 1, 453600, 5108114880, 131993382447360, 3463115239584000000
Offset: 0

Author

María Merino, Imanol Unanue, May 24 2017

Keywords

Comments

Computed using Polya's enumeration theorem for coloring.

Examples

			For n = 3 and m = 3 the T(3,3) = 90720 solutions are colorings of 3 X 3 matrices in 9 colors inequivalent under the action of the Klein group with exactly 1 occurrence of each color (coefficient of x1^1, x2^1, x3^1, x4^1, x5^1, x6^1, x7^1, x8^1, x9^1).
Triangle begins:
===================================================================
n\m | 0  1  2       3           4                5
----|--------------------------------------------------------------
0   | 1
1   | 1  1
2   | 1  1  1
3   | 1  1  1       90720
4   | 1  1  1       14968800    40864824000
5   | 1  1  453600  5108114880  131993382447360  3463115239584000000
		

Formula

G.f.: g(x1,x2,x3,x4,x5,x6,x7,x8,x9) = (y1^(m*n) + 3*y2^(m*n/2))/4 for even n and m; (y1^(m*n) + y1^n*y2^((m*n-m)/2) + 2*y2^(m*n/2))/4 for odd n and even m; (y1^(m*n) + y1^m*y2^((m*n-n)/2) + 2*y2^(m*n/2))/4 for even n and odd m; (y1^(m*n) + y1^n*y2^((m*n-n)/2) + y1^m*y2^((m*n-m)/2) + y1*y2^((m*n-1)/2))/4 for odd n and m; where the coefficients y1 and y2 correspond to y1 = Sum_{i=1..9} x_i and y2 = Sum_{i=1..9} x_i^2. Occurrences of numbers are ceiling(m*n/9) for the first k numbers and floor(m*n/9) for the last (9-k) numbers, if m*n = k mod 9.

A287378 Triangle read by rows: T(n,m) is the number of inequivalent n X m matrices under action of the Klein group, with one-eighth each of 1's, 2's, 3's, 4's, 5's, 6's, 7's and 8's (ordered occurrences rounded up/down if n*m != 0 mod 8).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 45360, 1, 1, 10080, 7484544, 20432442240, 1, 1, 226800, 2554075440, 29331862801920, 577185873264000000
Offset: 0

Author

María Merino, Imanol Unanue, May 24 2017

Keywords

Comments

Computed using Polya's enumeration theorem for coloring.

Examples

			For n = 4 and m = 2, the T(4,2) = 10080 solutions are colorings of 4 X 2 matrices in 8 colors inequivalent under the action of the Klein group with exactly 1 occurrence of each color (coefficient of x1^1, x2^1, x3^1, x4^1, x5^1, x6^1, x7^1, x8^1).
Triangle begins:
=================================================================
n\m | 0  1  2       3           4               5
----|------------------------------------------------------------
0   | 1
1   | 1  1
2   | 1  1  1
3   | 1  1  1       45360
4   | 1  1  10080   7484544     20432442240
5   | 1  1  226800  2554075440  29331862801920  577185873264000000
		

Formula

g(x1,x2,x3,x4,x5,x6,x7,x8) = (y1^(m*n) + 3*y2^(m*n/2))/4 for even n and m;
(y1^(m*n) + y1^n*y2^((m*n-m)/2) + 2*y2^(m*n/2))/4 for odd n and even m;
(y1^(m*n) + y1^m*y2^((m*n-n)/2) + 2*y2^(m*n/2))/4 for even n and odd m;
(y1^(m*n) + y1^n*y2^((m*n-n)/2) + y1^m*y2^((m*n-m)/2) + y1*y2^((m*n-1)/2))/4 for odd n and m, where the coefficients y1 and y2 correspond to y1 = Sum_{i=1..8} x_i and y2 = Sum_{i=1..8} x_i^2. Occurrences of numbers are ceiling(m*n/8) for the first k numbers and floor(m*n/8) for the last (8-k) numbers, if m*n = k mod 8.

A287377 Triangle read by rows: T(n,m) is the number of inequivalent n X m matrices under action of the Klein group, with one-seventh each of 1's, 2's, 3's, 4's, 5's, 6's and 7's (ordered occurrences rounded up/down if n*m != 0 mod 7).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 22680, 1, 1, 5040, 3742560, 4540536000, 1, 1, 113400, 851370480, 6518191680000, 54111175679736000
Offset: 0

Author

María Merino, Imanol Unanue, May 24 2017

Keywords

Comments

Computed using Polya's enumeration theorem for coloring.

Examples

			For n = 4 and m = 2 the T(4,2) = 5040 solutions are colorings of 4 X 2 matrices in 7 colors inequivalent under the action of the Klein group with exactly 2, 1, 1, 1, 1, 1, 1 occurrences of each color (coefficient of x1^2 x2^1 x3^1 x4^1 x5^1 x6^1 x7^1).
Triangle begins:
==============================================================
n\m | 0  1  2      3           4             5
----|---------------------------------------------------------
0   | 1
1   | 1  1
2   | 1  1  1
3   | 1  1  1       22680
4   | 1  1  5040    3742560    4540536000
5   | 1  1  113400  851370480  6518191680000  54111175679736000
		

Formula

g(x1,x2,x3,x4,x5,x6,x7)=(y1^(m*n) + 3*y2^(m*n/2))/4 for even n and m;
(y1^(m*n) + y1^n*y2^((m*n-m)/2) + 2*y2^(m*n/2))/4 for odd n and even m;
(y1^(m*n) + y1^m*y2^((m*n-n)/2) + 2*y2^(m*n/2))/4 for even n and odd m; (y1^(m*n) + y1^n*y2^((m*n-n)/2) + y1^m*y2^((m*n-m)/2) + y1*y2^((m*n-1)/2))/4 for odd n and m, where coefficient correspond to y1=Sum_{i=1..7} x_i, y2=Sum_{i=1..7} x_i^2, and occurrences of numbers are ceiling(m*n/7) for the first k numbers and floor(m*n/7) for the last (7-k) numbers, if m*n = k mod 7.

A287261 Number of inequivalent n X n matrices over an alphabet of size 10 under action of dihedral group of the square D_4, with one-tenth of 1's, 2's, 3's, 4's, 5's, 6's, 7's, 8's, 9's and 0's (ordered occurrences rounded up/down if n^2 != 0 mod 10).

Original entry on oeis.org

1, 1, 1, 1, 40864828320, 7792009289281728000, 187746872107299580970294400000, 614005731326101652800803825889630961295360, 176445174659483893854948844253232539237396497554309120000, 7090469783239448892319287907564531885316857076509137838529329991091840000
Offset: 0

Author

María Merino, Imanol Unanue, May 22 2017

Keywords

Comments

Computed using Polya's enumeration theorem for coloring.

Examples

			For n = 3 the a(4) = 40864828320 solutions are colorings of 4 X 4 matrices in 10 colors inequivalent under the action of D_4 with exactly occurrences 2, 2, 2, 2, 2, 2, 1, 1, 1, 1 of each color (coefficient of x1^2 x2^2 x3^2 x4^2 x5^2 x6^2 x7^1 x8^1 x9^1 x10^1).
		

Formula

G.f.: g(x1,x2,x3,x4,x5,x6,x7,x8,x9,x10) = (1/8)*(y1^(n^2)+2*y1^n*y2^((n^2-n)/2)+3*y2^(n^2/2)+2*y4^(n^2/4)) if n even and (1/8)*(y1^(n^2)+4*y1^n*y2^((n^2-n)/2)+y1*y2^((n^2-1)/2)+2*y1*y4^((n^2-1)/4)) if n odd, where coefficient correspond to y1=Sum_{i=1..10} x_i, y2=Sum_{i=1..10} x_i^2, y4=Sum_{i=1..10} x_i^4 and occurrences of numbers are ceiling(n^2/10) for the first k numbers and floor(n^2/10) for the last (10-k) numbers, if n^2 = k mod 10.

A287250 Number of inequivalent n X n matrices over GF(9) under action of dihedral group of the square D_4, with one-ninth each of 1's, 2's, 3's, 4's, 5's, 6's, 7's, 8's and 9's (ordered occurrences rounded up/down if n^2 != 0 mod 9).

Original entry on oeis.org

1, 1, 1, 45360, 20432427120, 1731557619792000000, 17601269260059379482191694720, 11370476506038919496334983007474778275840, 944848320304251231447932170156537415535539635814400000, 6641336088298446224006555306105706090482482272285249518936232000000000
Offset: 0

Author

María Merino, Imanol Unanue, May 22 2017

Keywords

Comments

Computed using Polya's enumeration theorem for coloring.

Examples

			For n = 3 the a(3) = 45360 solutions are colorings of 3 X 3 matrices in 9 colors inequivalent under the action of D_4 with exactly 1 occurrence of each color (coefficient of x1^1 x2^1 x3^1 x4^1 x5^1 x6^1 x7^1 x8^1 x9^1).
		

Formula

G.f.: g(x1,x2,x3,x4,x5,x6,x7,x8,x9) = (1/8)*(y1^(n^2)+2*y1^n*y2^((n^2-n)/2)+3*y2^(n^2/2)+2*y4^(n^2/4)) if n even and (1/8)*(y1^(n^2)+4*y1^n*y2^((n^2-n)/2)+y1*y2^((n^2-1)/2)+2*y1*y4^((n^2-1)/4)) if n odd, where coefficient correspond to y1=Sum_{i=1..9} x_i, y2=Sum_{i=1..9} x_i^2, y4=Sum_{i=1..9} x_i^4 and occurrences of numbers are ceiling(n^2/9) for the first k numbers and floor(n^2/9) for the last (9-k) numbers, if n^2 = k mod 9.

A287249 Number of inequivalent n X n matrices over GF(8) under action of dihedral group of the square D_4, with one-eighth each of 1's, 2's, 3's, 4's, 5's, 6's, 7's and 8's (ordered occurrences rounded up/down if n^2 != 0 mod 8).

Original entry on oeis.org

1, 1, 1, 22680, 10216251360, 288592936632000000, 675888739586283307003920000, 150403128386758194407881602780164966400, 2270715491453850844620503532869818724155487772912000, 2190916399747036514334089808617857198357442887303702763561256837120
Offset: 0

Author

María Merino, Imanol Unanue, May 22 2017

Keywords

Comments

Computed using Polya's enumeration theorem for coloring.

Examples

			For n = 3 the a(4) = 10216251360 solutions are colorings of 4 X 4 matrices in 8 colors inequivalent under the action of D_4 with exactly 2 occurrences of each color (coefficient of x1^2 x2^2 x3^2 x4^2 x5^2 x6^2 x7^2 x8^2).
		

Formula

G.f.: g(x1,x2,x3,x4,x5,x6,x7,x8) = (1/8)*(y1^(n^2)+2*y1^n*y2^((n^2-n)/2)+3*y2^(n^2/2)+2*y4^(n^2/4)) if n even and (1/8)*(y1^(n^2)+4*y1^n*y2^((n^2-n)/2)+y1*y2^((n^2-1)/2)+2*y1*y4^((n^2-1)/4)) if n odd, where coefficient correspond to y1=Sum_{i=1..8} x_i, y2=Sum_{i=1..8} x_i^2, y4=Sum_{i=1..8} x_i^4 and occurrences of numbers are ceiling(n^2/8) for the first k numbers and floor(n^2/8) for the last (8-k) numbers, if n^2 = k mod 8.

A287245 Number of inequivalent n X n matrices over GF(7) under action of dihedral group of the square D_4, with one-seventh each of 1's, 2's, 3's, 4's, 5's, 6's and 7's (ordered occurrences rounded up/down if n^2 != 0 mod 7).

Original entry on oeis.org

1, 1, 1, 11340, 2270280240, 27055587870486000, 21628439666761521875561280, 920451958269648700957746787694592000, 1914192808178753950843058828570207003149548000000, 216425158352284448578663515683744576588775769063470820304640000
Offset: 0

Author

María Merino, Imanol Unanue, May 22 2017

Keywords

Comments

Computed using Polya's enumeration theorem for coloring.

Examples

			For n = 3 the a(3) = 11340 solutions are colorings of 3 X 3 matrices in 7 colors inequivalent under the action of D_4 with exactly occurrences 2, 2, 1, 1, 1, 1, 1 of each color (coefficient of x1^2 x2^2 x3^1 x4^1 x5^1 x6^1 x7^1).
		

Formula

G.f.: g(x1,x2,x3,x4,x5,x6,x7)=1/8*(y1^(n^2)+2*y1^n*y2^((n^2-n)/2)+3*y2^(n^2/2)+2*y4^(n^2/4)) if n even and 1/8*(y1^(n^2)+4*y1^n*y2^((n^2-n)/2)+y1*y2^((n^2-1)/2)+2*y1*y4^((n^2-1)/4)) if n odd, where coefficient correspond to y1=Sum_{i=1..7} x_i, y2=Sum_{i=1..7} x_i^2, y4=Sum_{i=1..7} x_i^4 and occurrences of numbers are ceiling(n^2/7) for the first k numbers and floor(n^2/7) for the last (7-k) numbers, if n^2 = k mod 7.

A287239 Number of inequivalent n X n matrices over an alphabet of size 6 under action of dihedral group of the square D_4, with one-sixth each of 1s, 2s, 3s, 4s, 5s and 6s (ordered occurrences rounded up/down if n^2 != 0 mod 6).

Original entry on oeis.org

1, 1, 1, 5688, 504508320, 2029169127793680, 333772217080092664473600, 1966297518276227170017585421188600, 474436367892839446541884570454351985506872320, 4529567636413022031420100639004131328550592354551163392000, 1664947024157601976065851576560401128416782438266187161307818265349050000
Offset: 0

Author

María Merino, Imanol Unanue, May 22 2017

Keywords

Comments

Computed using Polya's enumeration theorem for coloring.

Examples

			For n = 3 the a(3) = 5688 solutions are colorings of 3 X 3 matrices in 6 colors inequivalent under the action of D_4 with exactly 2 occurrences of each color (coefficient of x1^2 x2^2 x3^2 x4^2 x5^2 x6^2).
		

Crossrefs

Formula

G.f.: g(x1,x2,x3,x4,x5,x6)=1/8*(y1^(n^2)+2*y1^n*y2^((n^2-n)/2)+3*y2^(n^2/2)+2*y4^(n^2/4)) if n even and 1/8*(y1^(n^2)+4*y1^n*y2^((n^2-n)/2)+y1*y2^((n^2-1)/2)+2*y1*y4^((n^2-1)/4)) if n odd, where coefficient correspond to y1=Sum_{i=1..6} x_i, y2=Sum_{i=1..6} x_i^2, y4=Sum_{i=1..6} x_i^4 and occurrences of numbers are ceiling(n^2/6) for the first k numbers and floor(n^2/6) for the last (6-k) numbers, if n^2 = k mod 6.