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.

Previous Showing 11-20 of 95 results. Next

A028365 Order of general affine group over GF(2), AGL(n,2).

Original entry on oeis.org

1, 2, 24, 1344, 322560, 319979520, 1290157424640, 20972799094947840, 1369104324918194995200, 358201502736997192984166400, 375234700595146883504949480652800, 1573079924978208093254925489963584716800
Offset: 0

Views

Author

Keywords

Comments

For n > 0, a(n) = v(n+1)/v(n), where v = A203305 is the Vandermonde determinant of the first n of the numbers -2^j - 1; see the Mathematica section. - Clark Kimberling, Jan 01 2012

References

  • J. M. Borwein, D. H. Bailey and R. Girgensohn, Experimentation in Mathematics, A K Peters, Ltd., Natick, MA, 2004. x+357 pp. See p. 54 (1.64).

Crossrefs

Programs

  • Magma
    [1] cat [(&*[2^(n+1) - 2^(j+1): j in [0..n-1]]): n in [1..20]]; // G. C. Greubel, Aug 31 2023
    
  • Maple
    A028365 := n->2^n*product(2^n-2^'i','i'=0..n-1); # version 1
    A028365 := n->product(2^'j'-1,'j'=1..n)*2^binomial(n+1,2); # version 2
  • Mathematica
    RecurrenceTable[{a[1]==1, a[2]==2, a[3]==24, a[n]==(6a[n-1]^2 a[n-3] - 8a[n-1] a[n-2]^2)/(a[n-2] a[n-3])}, a[n], {n,20}] (* Harvey P. Dale, Aug 03 2011 *)
    (* Next, the connection with Vandermonde determinants *)
    f[j_]:= 2^j - 1; z = 15;
    v[n_]:= Product[Product[f[k] - f[j], {j,k-1}], {k,2,n}]
    Table[v[n], {n,z}]   (* A203303 *)
    Table[v[n+1]/v[n], {n,z}]  (* A028365 *)
    Table[v[n]*v[n+2]/(2*v[n+1])^2, {n,z}]  (* A171499 *) (* Clark Kimberling, Jan 01 2011 *)
    Table[(-1)^n*2^Binomial[n+1,2]*QPochhammer[2,2,n], {n,0,20}] (* G. C. Greubel, Aug 31 2023 *)
  • PARI
    a(n)=if(n<0,0,prod(k=1,n,2^k-1)*2^((n^2+n)/2)) /* Michael Somos, May 09 2005 */
    
  • SageMath
    [product(2^(n+1) - 2^(k+1) for k in range(n)) for n in range(21)] # G. C. Greubel, Aug 31 2023

Formula

a(n) is asymptotic to C*2^(n*(n+1)) where C = 0.288788095086602421278899721... = prod(k>=1, 1-1/2^k) (cf. A048651). - Benoit Cloitre, Apr 11 2003
a(n) = (6*a(n-1)^2*a(n-3) - 8*a(n-1)*a(n-2)^2) / (a(n-2)*a(n-3)). [From Putman Exam]. - Max Alekseyev, May 18 2007
a(n) = 2*A203305(n), n > 0. - Clark Kimberling, Jan 01 2012
From Max Alekseyev, Jun 09 2015: (Start)
a(n) = 2^A000217(n) * A005329(n).
a(n) = 2^n * A002884(n).
a(n) = 2^n * n! * A053601(n). (End)
From G. C. Greubel, Aug 31 2023: (Start)
a(n) = Product_{j=0..n-1} (2^(n+1) - 2^(j+1)).
a(n) = (-1)^n * 2^binomial(n+1,2) * QPochhammer(2,2,n). (End)

A046747 Number of n X n rational {0,1}-matrices of determinant 0.

Original entry on oeis.org

1, 10, 338, 42976, 21040112, 39882864736, 292604283435872, 8286284310367538176
Offset: 1

Views

Author

Günter M. Ziegler (ziegler(AT)math.tu-berlin.de)

Keywords

Examples

			a(2)=10: the matrix of all 0's, 4 matrices with 2 zeros in the same row or column, 4 matrices with 3 zeros and the all-1 matrix.
		

Crossrefs

Programs

  • Mathematica
    Sum[KroneckerDelta[Det[Array[Mod[Floor[k/(2^(n*(#1-1)+#2-1))],2]&,{n,n}]],0],{k,0,(2^(n^2))-1}] (* John M. Campbell, Jun 24 2011 *)
    Count[Det /@ Tuples[{0, 1}, {n, n}], 0] (* David Trimas, Sep 23 2024 *)
  • PARI
    A046747(n) = m=matrix(n,n); ct=0; for(x=0,2^(n*n)-1,a=binary(x+2^(n*n)); for(i=1,n, for(j=1,n,m[i,j]=a[n*i+j+1-n])); if(matdet(m)==0,ct=ct+1,); ); ct \\ Randall L Rathbun
    
  • PARI
    a(n)=sum(i=0,2^n^2-1,matdet(matrix(n,n,x,y,(i>>(n*x+y-n-1))%2))==0) \\ Charles R Greathouse IV, Feb 21 2015

Formula

a(n) = 2^(n^2) - n! * binomial(2^n -1, n) + n! * A000410(n).
a(n) + A055165(n) = 2^(n^2) = total number of n X n (0, 1) matrices.
The probability that a random n X n {0,1}-matrix is singular is conjectured to be asymptotic to C(n+1, 2)*(1/2)^(n-1). [Corrected by N. J. A. Sloane, Jan 02 2007]

Extensions

a(8) from Vladeta Jovovic, Mar 28 2006

A053291 Nonsingular n X n matrices over GF(4).

Original entry on oeis.org

1, 3, 180, 181440, 2961100800, 775476766310400, 3251791214634074112000, 218210695042457748180566016000, 234298374547168764346587444978647040000, 4025200069765920285793155323595159699896401920000, 1106437515026051855463365435310419366987397763763798016000000
Offset: 0

Views

Author

Stephen G Penrice, Mar 04 2000

Keywords

Crossrefs

Programs

  • Magma
    [1] cat [&*[(4^n - 4^k): k in [0..n-1]]: n in [1..8]]; // Bruno Berselli, Jan 28 2013
    
  • Mathematica
    Table[Product[4^n - 4^k, {k,0,n-1}], {n,0,10}] (* Geoffrey Critzer, Jan 26 2013 *)
  • PARI
    for(n=0,10, print1(prod(k=0,n-1, 4^n - 4^k), ", ")) \\ G. C. Greubel, May 31 2018

Formula

a(n) = (4^n - 1)*(4^n - 4)*...*(4^n - 4^(n-1)).
a(n) = A053763(n)*A027637(n). - Bruno Berselli, Jan 30 2013
From Amiram Eldar, Jul 06 2025: (Start)
a(n) = Product_{k=1..n} A115490(k).
a(n) ~ c * 4^(n^2), where c = A100221. (End)

Extensions

More terms from Vladeta Jovovic, Mar 16 2000

A053601 Number of bases of an n-dimensional vector space over GF(2).

Original entry on oeis.org

1, 1, 3, 28, 840, 83328, 27998208, 32509919232, 132640470466560, 1927943976061501440, 100981078400558897823744, 19242660536873338307044442112, 13448310596010038676027219703234560, 34707333779115158227208335860718444216320, 332718225878012276874300952228513073208156487680
Offset: 0

Views

Author

Fred Galvin (galvin(AT)math.ukans.edu), Jan 20 2000

Keywords

Examples

			a(2)=3 because the 3 bases are {01,10}, {01,11}, {10,11}.
		

References

  • R. Lidl and H. Niederreiter, Introduction to Finite Fields and Their Applications, Cambridge 1986

Crossrefs

Cf. A002884.

Programs

  • Magma
    [1] cat [(&*[2^n -2^k: k in [0..n-1]])/Factorial(n): n in [1..20]]; // G. C. Greubel, May 16 2019
    
  • Mathematica
    Table[Product[2^n - 2^k, {k,0,n-1}]/n!, {n,0,20}] (* G. C. Greubel, May 16 2019 *)
  • PARI
    a(n) = prod(k=0, n-1, 2^n - 2^k)/n!; \\ Michel Marcus, Mar 25 2016
    
  • Sage
    [product(2^n -2^k for k in (0..n-1))/factorial(n) for n in (0..20)] # G. C. Greubel, May 16 2019

Formula

a(n) = (2^n-1)(2^n-2)...(2^n-2^(n-1))/n! = A002884(n)/n!.

Extensions

More terms from Vladeta Jovovic, Apr 05 2000

A053292 Number of nonsingular n X n matrices over GF(5).

Original entry on oeis.org

1, 4, 480, 1488000, 116064000000, 226614960000000000, 11064475422000000000000000, 13506266841692625000000000000000000, 412177498341354683437500000000000000000000000
Offset: 0

Views

Author

Stephen G Penrice, Mar 04 2000

Keywords

Crossrefs

Programs

  • Magma
    [1] cat [&*[(5^n - 5^k): k in [0..n-1]]: n in [1..8]]; // Bruno Berselli, Jan 28 2013
    
  • Mathematica
    Table[Product[5^n - 5^k, {k,0,n-1}], {n,0,10}] (* Geoffrey Critzer, Jan 26 2013 *)
  • PARI
    for(n=0,10, print1(prod(k=0,n-1, 5^n - 5^k), ", ")) \\ G. C. Greubel, May 31 2018

Formula

a(n) = (5^n - 1)*(5^n - 5)*...*(5^n - 5^(n-1)).
a(n) = A109345(n)*A027872(n). - Bruno Berselli, Jan 30 2013
a(n) ~ c * 5^(n^2), where c = A100222. - Amiram Eldar, Jul 06 2025

Extensions

More terms from Vladeta Jovovic, Mar 16 2000

A053293 Number of nonsingular n X n matrices over GF(7).

Original entry on oeis.org

1, 6, 2016, 33784128, 27811094169600, 1122211189922928537600, 2218959336124989671614429593600, 214992513152176999576908105619651923148800, 1020690003311610463765638355505358381593396977336320000, 237443634207909205360438080389756681126654524500073656592021585920000
Offset: 0

Views

Author

Stephen G Penrice, Mar 04 2000

Keywords

Crossrefs

Programs

  • Magma
    [1] cat [&*[(7^n - 7^k): k in [0..n-1]]: n in [1..7]]; // Bruno Berselli, Jan 28 2013
    
  • Mathematica
    Table[Product[7^n - 7^k, {k, 0, n-1}], {n, 0, 10}] (* Vincenzo Librandi, Jan 28 2013 *)
  • PARI
    for(n=0,10, print1(prod(k=0,n-1, 7^n - 7^k), ", ")) \\ G. C. Greubel, May 31 2018

Formula

a(n) = (7^n - 1)*(7^n - 7)*...*(7^n - 7^(n-1)).
a(n) = A109493(n)*A027875(n). - Bruno Berselli, Jan 30 2013
a(n) ~ c * 7^(n^2), where c = A132035. - Amiram Eldar, Jul 06 2025

Extensions

More terms from Vladeta Jovovic, Mar 16 2000

A132186 Number of idempotent n X n matrices over GF(2); also number of diagonalizable n X n matrices over GF(2).

Original entry on oeis.org

1, 2, 8, 58, 802, 20834, 1051586, 102233986, 19614424834, 7355623374338, 5494866505497602, 8087844439442585602, 23834930674299549249538, 138978138716920276085366786, 1626809921636911219317749563394, 37757678575184051755732304668884994
Offset: 0

Views

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 19 2003 and Vladeta Jovovic, Nov 04 2007

Keywords

Crossrefs

Row sums of A296548.

Programs

  • Maple
    T:= proc(n, k) option remember; `if`(k<0 or k>n, 0,
          `if`(n=0, 1, T(n-1, k-1)+2^k*T(n-1, k)))
        end:
    a:= n-> add(2^(k*(n-k))*T(n, k), k=0...n):
    seq(a(n), n=0..20);  # Alois P. Heinz, Aug 06 2017
  • Mathematica
    nn = 10; g[n_] := (q - 1)^n  q^Binomial[n, 2] FunctionExpand[
    QFactorial[n, q]] /. q -> 2; G[z_] := Sum[z^k/g[k], {k, 0, nn}];Table[g[n], {n, 0, nn}] CoefficientList[Series[G[z]^2, {z, 0, nn}], z] (* Geoffrey Critzer, Aug 04 2017 *)
    a[n_] := Block[{m}, Length@ Select[ Range[2^(n^2)], (m = Partition[ IntegerDigits[ #-1, 2, n^2], n]; Mod[m.m, 2] == m) &]]; a /@ Range[4] (* Giovanni Resta, Apr 09 2017 *)

Formula

a(n) = sum(k=0...n, 2^(k(n-k))*[n,k]2), where [n,k]_2 is the Gaussian binomial for q=2. - _Marc van Leeuwen, May 22 2013
a(n)/A002884(n) is the coefficient of x^n in (Sum_{n>=0} x^n/A002884(n))^2. - Geoffrey Critzer, Aug 04 2017
a(n) ~ c * 2^(n^2/2), where c = EllipticTheta(3, 0, 1/4) / QPochhammer(1/2) = 5.221199057419682876170323638731707664618893... if n is even and c = EllipticTheta(2, 0, 1/4) / QPochhammer(1/2) = 5.2043255482837364968664526298606149440286... if n is odd. - Vaclav Kotesovec, Jun 09 2025

Extensions

This is the result of merging two independently submitted but identical sequences. Thanks to Geoffrey Critzer for suggesting this. - N. J. A. Sloane, Dec 26 2017

A002820 Number of n X n invertible binary matrices A such that A+I is invertible.

Original entry on oeis.org

1, 0, 2, 48, 5824, 2887680, 5821595648, 47317927329792, 1544457148312846336, 202039706313624586813440, 105823549214125066767168438272, 221819704567105547916502447159246848, 1860304261534304703934696550224148083769344, 62413833036707798343389591015829588620560344023040
Offset: 0

Views

Author

Keywords

Comments

Also number of linear orthomorphisms of GF(2)^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

Cf. A002884.
Column k=0 of A346201 and of A346381.

Programs

  • Maple
    # (Maple program based on Dai et al. from N. J. A. Sloane, Aug 10 2011)
    N:=proc(n,i) option remember; if i = 1 then 1 else (2^n-2^(i-1))*N(n,i-1); fi; end;
    Oh:=proc(n) option remember; local r; global N;
    if n=0 then RETURN(1) elif n=1 then RETURN(0) else
    add( 2^(r-2)*N(n,r)*2^(r*(n-r))*Oh(n-r), r=2..n); fi; end;
    [seq(Oh(n),n=0..15)];
  • Mathematica
    ni[n_, i_] := ni[n, i] = If[i == 1, 1, (2^n - 2^(i-1))*ni[n, i-1]]; a[0] = 1; a[1] = 0; a[n_] := a[n] = Sum[ 2^(r-2)*ni[n, r]*2^(r*(n-r))*a[n-r], {r, 2, n}]; Table[a[n], {n, 1, 11}] (* Jean-François Alcover, Jan 19 2012, after Maple *)

Formula

Reference gives a recurrence.
a(n) = 2^(n(n-1)/2) * A005327(n+1).

Extensions

More terms from Vladeta Jovovic, Mar 17 2000
Entry revised by N. J. A. Sloane, Aug 10 2011
a(0)=1 prepended by Alois P. Heinz, Jan 10 2025

A316622 Array read by antidiagonals: T(n,k) is the order of the group GL(n,Z_k).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 6, 1, 1, 2, 48, 168, 1, 1, 4, 96, 11232, 20160, 1, 1, 2, 480, 86016, 24261120, 9999360, 1, 1, 6, 288, 1488000, 1321205760, 475566474240, 20158709760, 1, 1, 4, 2016, 1886976, 116064000000, 335522845163520, 84129611558952960, 163849992929280, 1
Offset: 0

Views

Author

Andrew Howroyd, Jul 08 2018

Keywords

Comments

All rows are multiplicative.
Equivalently, the number of invertible n X n matrices mod k.
Also, for k prime (but not higher prime powers) the number of nonsingular n X n matrices over GF(k).
For k >= 2, n! divides T(n,k) since the subgroup of GL(n,k) consisting of all permutation matrices is isomorphic to S_n (the n-th symmetric group). Note that a permutation matrix is an orthogonal matrix, hence having determinant +-1. - Jianing Song, Oct 29 2022

Examples

			Array begins:
=================================================================
n\k| 1       2         3          4             5           6
---+-------------------------------------------------------------
0  | 1       1         1          1            1            1 ...
1  | 1       1         2          2            4            2 ...
2  | 1       6        48         96          480          288 ...
3  | 1     168     11232      86016      1488000      1886976 ...
4  | 1   20160  24261120 1321205760 116064000000 489104179200 ...
5  | 1 9999360  ...
...
		

Crossrefs

Rows n=2..4 are A000252, A064767, A305186.
Columns k=2..7 are A002884, A053290, A065128, A053292, A065498, A053293.
Cf. A053291 (GF(4)), A052496 (GF(8)), A052497 (GF(9)).
Cf. A316623.

Programs

  • GAP
    T:=function(n,k) if k=1 or n=0 then return 1; else return Order(GL(n, Integers mod k)); fi; end;
    for n in [0..5] do Print(List([1..6], k->T(n,k)), "\n"); od;
    
  • Mathematica
    T[, 1] = T[0, ] = 1; T[n_, k_] := T[n, k] = Module[{f = FactorInteger[k], p, e}, If[Length[f] == 1, {p, e} = f[[1]]; (p^e)^(n^2)* Product[(1 - 1/p^j), {j, 1, n}], Times @@ (T[n, Power @@ #]& /@ f)]];
    Table[T[n - k + 1, k], {n, 0, 8}, {k, n + 1, 1, -1}] // Flatten (* Jean-François Alcover, Jul 25 2019 *)
  • PARI
    T(n,k)={my(f=factor(k)); k^(n^2) * prod(i=1, #f~, my(p=f[i,1]); prod(j=1, n, (1 - p^(-j))))}

Formula

T(n,p^e) = (p^e)^(n^2) * Product_{j=1..n} (1 - 1/p^j) for prime p.

A171499 a(n) = 6*a(n-1) - 8*a(n-2) for n > 1; a(0) = 3, a(1) = 14.

Original entry on oeis.org

3, 14, 60, 248, 1008, 4064, 16320, 65408, 261888, 1048064, 4193280, 16775168, 67104768, 268427264, 1073725440, 4294934528, 17179803648, 68719345664, 274877644800, 1099511103488, 4398045462528, 17592183947264, 70368739983360
Offset: 0

Views

Author

Klaus Brockhaus, Dec 10 2009

Keywords

Comments

Binomial transform of A171498; second binomial transform of A171497; third binomial transform of A010703.
Related to sequences A001969 and A000069, sum of each group with exponent 1. - Eric Desbiaux, Jul 24 2013
a(n) in base 2 is n+2 1s followed by n 0s. - Hussam al-Homsi, Oct 12 2021

Crossrefs

Programs

  • Magma
    [4*4^n-2^n: n in [0..30]]; // Vincenzo Librandi, Jul 18 2011
    
  • Mathematica
    (* This program shows how A171499 arises from the Vandermonde determinant of (1,2,4,...,2^(n-1)). *)
    f[j_]:= 2^j - 1; z = 15;
    v[n_]:= Product[Product[f[k] - f[j], {j,k-1}], {k,2,n}]
    d[n_]:= Product[(i-1)!, {i,n}]
    Table[v[n], {n,z}]                     (* A203303 *)
    Table[v[n+1]/v[n], {n,z}]              (* A002884 *)
    Table[v[n]*v[n+2]/(2*v[n+1])^2, {n,z}]  (* A171499 *)
    (* Clark Kimberling, Jan 02 2011 *)
    LinearRecurrence[{6,-8},{3,14},30] (* Harvey P. Dale, Sep 05 2021 *)
  • PARI
    {m=23; v=concat([3, 14], vector(m-2)); for(n=3, m, v[n]=6*v[n-1]-8*v[n-2]); v}
    
  • SageMath
    [4^(n+1) -2^n for n in range(31)] # G. C. Greubel, Aug 31 2023

Formula

a(n) = 4*4^n - 2^n = 2^n * (2^(n+2) - 1).
G.f.: (3-4*x)/((1-2*x)*(1-4*x)).
a(n) = 4*a(n-1) + 2^n for n > 0. - Vincenzo Librandi, Jul 18 2011
a(n) = A171476(n+1)/2. - Hussam al-Homsi, Jun 06 2021
E.g.f.: 4*exp(4*x) - exp(2*x). - G. C. Greubel, Aug 31 2023
Previous Showing 11-20 of 95 results. Next