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 16 results. Next

A002884 Number of nonsingular n X n matrices over GF(2) (order of the group GL(n,2)); order of Chevalley group A_n (2); order of projective special linear group PSL_n(2).

Original entry on oeis.org

1, 1, 6, 168, 20160, 9999360, 20158709760, 163849992929280, 5348063769211699200, 699612310033197642547200, 366440137299948128422802227200, 768105432118265670534631586896281600, 6441762292785762141878919881400879415296000, 216123289355092695876117433338079655078664339456000
Offset: 0

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Author

Keywords

Comments

Also number of bases for GF(2^n) over GF(2).
Also (apparently) number of n X n matrices over GF(2) having permanent = 1. - Hugo Pfoertner, Nov 14 2003
The previous comment is true because over GF(2) permanents and determinants are the same. - Joerg Arndt, Mar 07 2008
The number of automorphisms of (Z_2)^n (the direct product of n copies of Z_2). - Peter Eastwood, Apr 06 2015
Note that n! divides a(n) since the subgroup of GL(n,2) consisting of all permutation matrices is isomorphic to S_n (the n-th symmetric group). - Jianing Song, Oct 29 2022
The number of boolean operations on n bits, or quantum operations on n qubits, that can be constructed using only CNOT (controlled NOT) gates. - David Radcliffe, Jul 06 2025

Examples

			PSL_2(2) is isomorphic to the symmetric group S_3 of order 6.
		

References

  • Roger W. Carter, Simple groups of Lie type. Pure and Applied Mathematics, Vol. 28, John Wiley & Sons, London-New York-Sydney, 1972. viii+331pp. MR0407163 (53 #10946). See page 2.
  • J. H. Conway, R. T. Curtis, S. P. Norton, R. A. Parker and R. A. Wilson, ATLAS of Finite Groups. Oxford Univ. Press, 1985 [for best online version see https://oeis.org/wiki/Welcome#Links_to_Other_Sites], p. xvi.
  • H. S. M. Coxeter and W. O. J. Moser, Generators and Relations for Discrete Groups, 4th ed., Springer-Verlag, NY, reprinted 1984, p. 131.
  • K. J. Horadam, Hadamard matrices and their applications. Princeton University Press, Princeton, NJ, 2007. xiv+263 pp. See p. 132.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Column k=2 of A316622 and A316623.
Cf. A006516, A048651, A203303. Row sums of A381854.

Programs

  • Magma
    [1] cat [(&*[2^n -2^k: k in [0..n-1]]): n in [1..15]]; // G. C. Greubel, Aug 31 2023
    
  • Maple
    # First program
    A002884:= n-> mul(2^n - 2^i, i=0..n-1);
    seq(A002884(n), n = 0..12);
    # Second program
    A002884:= n-> 2^(n*(n-1)/2) * mul( 2^i - 1, i=1..n);
    seq(A002884(n), n=0..12);
  • Mathematica
    Table[Product[2^n-2^i,{i,0,n-1}],{n,0,13}] (* Harvey P. Dale, Aug 07 2011 *)
    Table[2^(n*(n-1)/2) QPochhammer[2, 2, n] // Abs, {n, 0, 11}] (* Jean-François Alcover, Jul 15 2017 *)
  • PARI
    a(n)=prod(i=2,n,2^i-1)<Charles R Greathouse IV, Jan 13 2012
    
  • SageMath
    [product(2^n -2^j for j in range(n)) for n in range(16)] # G. C. Greubel, Aug 31 2023

Formula

a(n) = Product_{i=0..n-1} (2^n-2^i).
a(n) = 2^(n*(n-1)/2) * Product_{i=1..n} (2^i - 1).
a(n) = A203303(n+1)/A203303(n). - R. J. Mathar, Jan 06 2012
a(n) = (6*a(n-1)^2*a(n-3) - 8*a(n-1)*a(n-2)^2) / (a(n-2)*a(n-3)) for n > 2. - Seiichi Manyama, Oct 20 2016
a(n) ~ A048651 * 2^(n^2). - Vaclav Kotesovec, May 19 2020
a(n) = A006125(n) * A005329(n). - John Keith, Jun 30 2021
a(n) = Product_{k=1..n} A006516(k). - Amiram Eldar, Jul 06 2025

A055165 Number of invertible n X n matrices with entries equal to 0 or 1.

Original entry on oeis.org

1, 1, 6, 174, 22560, 12514320, 28836612000, 270345669985440, 10160459763342013440
Offset: 0

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Author

Ulrich Hermisson (uhermiss(AT)server1.rz.uni-leipzig.de), Jun 18 2000

Keywords

Comments

All eigenvalues are nonzero.

Examples

			For n=2 the 6 matrices are {{{0, 1}, {1, 0}}, {{0, 1}, {1, 1}}, {{1, 0}, {0, 1}}, {{1, 0}, {1, 1}}, {{1, 1}, {0, 1}}, {{1, 1}, {1, 0}}}.
		

Crossrefs

Cf. A056990, A056989, A046747, A055165, A002416, A003024 (positive definite matrices).
A046747(n) + a(n) = 2^(n^2) = total number of n X n (0, 1) matrices = sequence A002416.
Main diagonal of A064230.

Programs

  • PARI
    a(n)=sum(t=0,2^n^2-1,!!matdet(matrix(n,n,i,j,(t>>(i*n+j-n-1))%2))) \\ Charles R Greathouse IV, Feb 09 2016
    
  • Python
    from itertools import product
    from sympy import Matrix
    def A055165(n): return sum(1 for s in product([0,1],repeat=n**2) if Matrix(n,n,s).det() != 0) # Chai Wah Wu, Sep 24 2021

Formula

For an asymptotic estimate see A046747. A002884 is a lower bound. A002416 is an upper bound.
a(n) = n! * A088389(n). - Gerald McGarvey, Oct 20 2007

Extensions

More terms from Miodrag Zivkovic (ezivkovm(AT)matf.bg.ac.rs), Feb 28 2006
Description improved by Jeffrey Shallit, Feb 17 2016
a(0)=1 prepended by Alois P. Heinz, Jun 18 2022

A000410 Number of singular n X n rational (0,1)-matrices.

Original entry on oeis.org

0, 0, 6, 425, 65625, 27894671, 35716401889, 144866174953833
Offset: 1

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Author

Keywords

Comments

Number of all n X n (0,1)-matrices having distinct, nonzero ordered rows and determinant 0 - compare A000409.
a(n) is the number of singular n X n rational {0,1}-matrices with no zero rows and with all rows distinct, up to permutation of rows and so a(n) = binomial(2^n-1,n) - A088389(n). Cf. A116506, A116507, A116527, A116532. - Vladeta Jovovic, Apr 03 2006

References

  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Formula

n! * a(n) = A046747(n) - 2^(n^2) + n! * binomial(2^n -1, n).

Extensions

n=7 term from Guenter M. Ziegler (ziegler(AT)math.TU-Berlin.DE)
a(8) from Vladeta Jovovic, Mar 28 2006

A000409 Singular n X n (0,1)-matrices: the number of n X n (0,1)-matrices having distinct, nonzero ordered rows, but having at least two equal columns or at least one zero column.

Original entry on oeis.org

0, 6, 350, 43260, 14591171, 14657461469, 46173502811223, 474928141312623525, 16489412944755088235117, 1985178211854071817861662307, 846428472480689964807653763864449, 1299141117072945982773752362381072143359, 7268140170419155675761326840423792818571154945, 149650282980396792665043455999899697765782372693740287
Offset: 2

Views

Author

Keywords

Comments

This is a lower bound for the set of all n X n (0,1)-matrices having distinct, nonzero ordered rows and determinant 0 (compare A000410).
Here ordered means that we take only one representative from the n! matrices obtained by all permutations of the distinct rows of an n X n matrix.
a(n) is also the number of sets of n distinct nonzero (0,1)-vectors in R^n that do not span R^n.

References

  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Magma
    [ -(&+[StirlingFirst(n+1,k+1)*Binomial(2^k-1,n): k in [0..n-1]]): n in [2..15]]; // G. C. Greubel, Jun 05 2020
    
  • Maple
    with(combinat): T := proc(n) -sum(stirling1(n+1,k+1)*binomial(2^k-1,n),k=0..n-1); end proc:
  • Mathematica
    a[n_] := -Sum[ StirlingS1[n+1, k+1]*Binomial[2^k-1, n], {k, 0, n-1}]; Table[a[n], {n, 2, 15}] (* Jean-François Alcover, Nov 21 2012, from formula *)
  • PARI
    a(n) = -sum(k=0, n-1, stirling(n+1, k+1, 1)*binomial(2^k-1, n)); \\ Michel Marcus, Jun 05 2020
    
  • Sage
    [sum((-1)^(n+k+1)*stirling_number1(n+1,k+1)*binomial(2^k-1,n) for k in (0..n-1)) for n in (2..15)] # G. C. Greubel, Jun 05 2020

Formula

a(n) = (-1)*Sum_{k=0..n-1} Stirling1(n+1, k+1)*binomial(2^k-1, n).
a(n) = binomial(2^n-1, n) - A094000(n). - Vladeta Jovovic, Nov 27 2005

Extensions

Edited by W. Edwin Clark, Nov 02 2003

A056989 Number of nonsingular n X n (-1,0,1)-matrices (over the reals).

Original entry on oeis.org

1, 2, 48, 11808, 27947520, 609653621760, 119288919620689920
Offset: 0

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Author

Keywords

Comments

It would be nice to have an estimate for the asymptotic rate of growth.

Examples

			a(1) = 2: [1], [ -1].
a(2) = 48: There are 8 choices for the first column, u (say) and then the 2nd column can be anything except 0, u, -u, so 6 choices, giving a total of 8*6 = 48.
		

Crossrefs

Programs

  • Mathematica
    (* A brute force solution up to n = 4 *) a[n_] := a[n] = (m = Array[x, {n, n}]; cnt = 0; iter = {#, -1, 1}& /@ Flatten[m]; Do[ If[ Det[m] != 0, cnt++], Evaluate[ Sequence @@ iter]]; cnt); Table[ Print[a[n]]; a[n], {n, 1, 4}] (* Jean-François Alcover, Oct 11 2012 *)

Formula

a(n) = A060722(n) - A057981(n). - Alois P. Heinz, Dec 02 2019

Extensions

a(4) from Winston C. Yang (winston(AT)cs.wisc.edu), Aug 27 2000
Entry revised by N. J. A. Sloane, Jan 02 2007
a(5) from Giovanni Resta, Feb 20 2009
a(0)=1 prepended by Alois P. Heinz, Dec 02 2019
a(0)-a(5) confirmed and a(6) added by Minfeng Wang, May 01 2024

A064230 Triangle T(n,k) = number of rational (0,1) matrices of rank k (n >= 0, 0 <= k <= n).

Original entry on oeis.org

1, 1, 1, 1, 9, 6, 1, 49, 288, 174, 1, 225, 6750, 36000, 22560, 1, 961, 118800, 3159750, 17760600, 12514320, 1, 3969, 1807806, 190071000, 5295204600, 34395777360, 28836612000, 1, 16129, 25316928, 9271660734, 1001080231200, 32307576315840
Offset: 0

Views

Author

N. J. A. Sloane, Sep 23 2001

Keywords

Comments

Rows add to 2^(n^2).
Komlos and later Kahn, Komlos and Szemeredi show that almost all such matrices are invertible.
Table 3 from M. Zivkovic, Classification of small (0,1) matrices (see link). - Vladeta Jovovic, Mar 28 2006

Examples

			Triangle T(n,k) begins:
  1;
  1,   1;
  1,   9,      6;
  1,  49,    288,     174;
  1, 225,   6750,   36000,    22560;
  1, 961, 118800, 3159750, 17760600, 12514320;
  ...
		

References

  • J. Kahn, J. Komlos and E. Szemeredi: On the probability that a random +-1 matrix is singular, J. AMS 8 (1995), 223-240.
  • J. Komlos, On the determinants of random matrices, Studia Sci. Math. Hungar., 3 (1968), 387-399.

Crossrefs

Main diagonal gives A055165.

Programs

  • PARI
    T=matrix(5,5); { for(n=0,4, mm=matrix(n,n); for(k=0,n,T[1+n,1+k]=0); forvec(x=vector(n*n,i,[0,1]), for(i=1,n, for(j=1,n,mm[i,j]=x[i+n*(j-1)])); T[1+n,1+matrank(mm)]++); for(k=0,n,print1(T[1+n,1+k], if(k
    				

Formula

Sum_{k=1..n} k * T(n,k) = A086875(n). - Alois P. Heinz, Jun 18 2022

Extensions

More terms and PARI code from Michael Somos, Sep 25 2001
6 more terms from Lambert Klasen (Lambert.Klasen(AT)gmx.net), Dec 17 2004
More terms from Vladeta Jovovic, Mar 28 2006

A086906 Number of symmetric singular n X n (0,1) matrices over the reals.

Original entry on oeis.org

1, 4, 32, 496, 14172, 816684, 87982904, 18748545824, 7565600671504, 5940152086634096
Offset: 1

Views

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 19 2003

Keywords

Crossrefs

Formula

a(n) = 2^(n*(n+1)/2) - A086899(n).

Extensions

W. Edwin Clark computed the first entries.
a(6)-a(7) from Giovanni Resta, May 08 2006
a(8)-a(10) from Max Alekseyev, Jun 17 2025

A051752 Number of n X n (real) {0,1}-matrices having determinant A003432(n).

Original entry on oeis.org

1, 1, 3, 3, 60, 3600, 529200, 75600, 195955200, 13716864000
Offset: 0

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Author

Keywords

Crossrefs

Extensions

a(5) = 3600 from Daniel P. Corson (danl(AT)MIT.EDU), Jan 09 2000
a(6) = 529200, a(7) = 75600 from Ulrich Hermisson (uhermiss(AT)rz.uni-leipzig.de), Feb 25 2003
More terms from Miodrag Zivkovic (ezivkovm(AT)matf.bg.ac.yu), Feb 28 2006
a(0)=1 prepended by Alois P. Heinz, Dec 20 2023

A064231 Triangle read by rows: T(n,k) = number of rational (+1,-1) matrices of rank k (n >= 1, 1 <= k <= n).

Original entry on oeis.org

2, 8, 8, 32, 288, 192, 128, 6272, 36864, 22272, 512, 115200, 3456000, 18432000, 11550720, 2048, 1968128, 243302400, 6471168000, 36373708800, 25629327360, 8192, 32514048, 14809546752, 1557061632000, 43378316083200, 281770208133120
Offset: 1

Views

Author

N. J. A. Sloane, Sep 23 2001

Keywords

Comments

Rows add to 2^(n^2) = A002416. - Jonathan Vos Post, Feb 27 2011
Komlos and later Kahn, Komlos and Szemeredi show that almost all such matrices are invertible.

Examples

			2; 8,8; 32,288,192; 128,6272,36864,22272; ...
		

References

  • J. Kahn, J. Komlos and E. Szemeredi: On the probability that a random +-1 matrix is singular, J. AMS 8 (1995), 223-240.
  • J. Komlos, On the determinants of random matrices, Studia Sci. Math. Hungar., 3 (1968), 387-399.

Crossrefs

Programs

  • PARI
    T=matrix(4,4); { for(n=1,4, mm=matrix(n,n); for(k=1,n, T[n,k]=0); forvec(x=vector(n*n,i,[0,1]), for(i=1,n, for(j=1,n,mm[i,j]=(-1)^x[i+n*(j-1)])); T[n,matrank(mm)]++); for(k=1,n,print1(T[n,k], if(k
    				

Extensions

More terms and PARI code from Michael Somos, Sep 25 2001
More terms from Vladeta Jovovic, Apr 02 2006
Offset changed to 1 by T. D. Noe, Mar 02 2011

A086264 Number of real {0,1} n X n matrices having determinant=1.

Original entry on oeis.org

1, 1, 3, 84, 10020, 4851360, 9240051240, 67745781734400, 1883481284085791040
Offset: 0

Views

Author

Hugo Pfoertner, Oct 05 2003

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := Module[{M, iter, cnt = 0}, M = Table[a[i, j], {i, 1, n}, {j, 1, n}]; iter = Thread[{Flatten[M], 0, 1}]; Do[If[Det[M] == 1, cnt++], Evaluate[Sequence @@ iter]]; cnt];
    Do[Print[n, " ", a[n]], {n, 1, 4}] (* Jean-François Alcover, Dec 09 2018 *)

Extensions

a(0)=1 prepended by Alois P. Heinz, Jun 18 2022
a(7) from Minfeng Wang, Feb 09 2023
a(8) from Minfeng Wang, Apr 26 2024
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