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 1-8 of 8 results.

A085000 Maximal determinant of an n X n matrix using the integers 1 to n^2.

Original entry on oeis.org

1, 10, 412, 40800, 6839492, 1865999570, 762150368499
Offset: 1

Views

Author

Robert G. Wilson v, Jun 16 2003

Keywords

Comments

Bounds for the next terms and the corresponding matrices are given by O. Gasper, H. Pfoertner and M. Sigg: 440960274696935 <= a(8) < 441077015225642, 346254605664223620 <= a(9) < 346335386150480625, 356944784622927045792 <= a(10) < 357017114947987625629. a(n) < sqrt(3*((n^5+n^4+n^3+n^2)/12)^n*(n^2+1)/(n+1)). - Hugo Pfoertner, Aug 15 2010
Improved lower bounds (private communication from Benjamin R. Buhrow, Dec 09 2019): a(8) >= 440970981670289, a(9) >= 346260899916111296. - Hugo Pfoertner, Jan 25 2021
Improved lower bound (private communication from Richard Gosiorovsky, Aug 18 2021): a(10) >= 356948996371054862392. - Hugo Pfoertner, Aug 24 2021

Examples

			The following 3 X 3 matrix is one of 36 whose determinant is 412 (there are also 36 whose determinant is -412):
   9 3 5
   4 8 1
   2 6 7
Results from a specially adapted hill-climbing algorithm strongly suggest that a(5) = 6839492. a(6) is at least 1862125166. Heuristically, a(n) is approximately 0.44*n^(2.06*n), suggesting that a(7) is close to 6.8*10^11. - Tim Paulden (timmy(AT)cantab.net), Sep 21 2003
a(5) confirmed by _Robert Israel_ and _Hugo Pfoertner_. A corresponding matrix is ((25 15 9 11 4) (7 24 14 3 17) (6 12 23 20 5) (10 13 2 22 19) (16 1 18 8 21) ). - _Hugo Pfoertner_, Sep 23 2003
a(6) found with FORTRAN program given at Pfoertner link. A corresponding matrix is ((36 24 21 17 5 8) ( 3 35 25 15 23 11) (13 7 34 16 10 31) (14 22 2 33 12 28) (20 4 19 29 32 6) (26 18 9 1 30 27) ). - _Hugo Pfoertner_, Sep 23 2003
a(7) is the determinant of the matrix ((46 42 15 2 27 24 18) (9 48 36 30 7 14 31) (39 11 44 34 13 29 5) (26 22 17 41 47 1 21) (20 8 40 6 33 23 45) (4 28 19 25 38 49 12) (32 16 3 37 10 35 43)). Although no proof for the optimality of a(7) is available, the results of an extensive computational search make the existence of a better solution extremely unlikely. A total of approximately 15 CPU years on SGI Origin 3000 and of 3.8 CPU years on SGI Altix 3000 computers was used for this result.
		

Crossrefs

Programs

  • Mathematica
    Needs["DiscreteMath`Combinatorica`"]; n=3; n2=n^2; dMax=0; mMax={}; p=Range[n2]; Do[m=Partition[p, n]; d=Det[m]; If[d>dMax, dMax=d; mMax=m]; p=NextPermutation[p], {k, n2!}]; {dMax, mMax} (* T. D. Noe *)
  • PARI
    vectomat(v)=my(n=sqrtint(#v));matrix(n,n,i,j,v[n*(i-1)+j])
    a(n)=my(m,t,M); n*=n; for(k=0,(n-1)!-1, t=matdet(M=vectomat(numtoperm(n,k))); if(abs(t)>m, m=abs(t); print(t" "M)));m \\ Charles R Greathouse IV, Sep 13 2013

Extensions

a(4) from Marsac Laurent (jko(AT)rox0r.net), Sep 15 2003
a(6) from Hugo Pfoertner, Sep 23 2003
Entry edited by N. J. A. Sloane, Nov 22 2006, to remove some erroneous entries. Further edits Nov 25 2006.
a(7) from Hugo Pfoertner, Jan 22 2008

A088216 Smallest nonnegative number not expressible as determinant of an n X n matrix with elements 1..n^2.

Original entry on oeis.org

0, 324, 38831, 6773999, 1859163031
Offset: 2

Views

Author

Hugo Pfoertner, Sep 23 2003

Keywords

Examples

			a(2)=0 because the 2 X 2 determinant of a matrix with entries that are permutations of 1,2,3,4 can only assume the values +-2,+-5,+-10.
		

Crossrefs

a(3)=A088214(1), a(4)=A088237(1), a(5)=A088238(1), a(6)=A325900(1).

Extensions

a(6) from Hugo Pfoertner, Sep 07 2019

A088217 Number of distinct values that can be assumed by the determinant of an n X n matrix whose entries are all permutations of the numbers 1..n^2.

Original entry on oeis.org

1, 6, 777, 79455, 13602389, 3722956267
Offset: 1

Views

Author

Hugo Pfoertner, Sep 23 2003

Keywords

Comments

a(5) = 1 + 2*(A085000(5) - (number of terms of A088238)).

Examples

			a(2)=6 because the determinants of the 24 2 X 2 matrices whose entries are all permutations of 1,2,3,4 can only assume the values -10,-5,-2,2,5,10.
		

Crossrefs

Programs

  • Fortran
    C See link given in A088238.
  • Mathematica
    f[n_] := (p = Permutations[ Table[i, {i, n^2}]]; Length[ Union[ Table[ Det[ Partition[ p[[i]], n]], {i, 1, (n^2)!}]]]) (* Robert G. Wilson v *)

Extensions

Minor edits and a(6) from Hugo Pfoertner, Sep 08 2019

A088215 (1/36)*number of ways to express n as the determinant of a 3 X 3 matrix with elements 1..9.

Original entry on oeis.org

76, 32, 18, 30, 14, 47, 30, 25, 10, 41, 20, 42, 32, 25, 16, 36, 14, 31, 39, 28, 35, 39, 20, 22, 18, 33, 19, 45, 12, 21, 37, 26, 15, 41, 25, 37, 29, 27, 18, 34, 22, 24, 23, 24, 17, 48, 16, 16, 18, 15, 25, 35, 16, 21, 36, 43, 11, 30, 5, 18, 31, 17, 13, 28, 11, 42, 35, 24, 13, 35
Offset: 0

Views

Author

Hugo Pfoertner, Sep 23 2003

Keywords

Comments

0 can be expressed in 36*76=2716 ways as the determinant of a 3 X 3 matrix which has elements 1..9. One such way is e.g. det ((1 2 3)(4 5 6)(7 8 9))=0. All numbers between -323 and +323 can be expressed by such a determinant. The first number not expressible is given by A088216.

Crossrefs

Cf. A136608 [analogous sequence for 4 X 4 matrices].

A088237 Numbers less than the maximum possible determinant A085000(4)=40800 not occurring as determinant of a 4 X 4 matrix with elements 1..16.

Original entry on oeis.org

38831, 38875, 38959, 38963, 39013, 39057, 39059, 39061, 39063, 39071, 39099, 39109, 39111, 39125, 39137, 39154, 39155, 39178, 39190, 39191, 39205, 39223, 39245, 39247, 39251, 39254, 39267, 39274, 39277, 39279, 39281, 39297, 39310
Offset: 1

Views

Author

Hugo Pfoertner, Sep 25 2003

Keywords

Crossrefs

Extensions

Full sequence from Hugo Pfoertner, Aug 31 2014

A325900 Numbers less than the maximum possible determinant A085000(6)=1865999570 not occurring as determinant of a 6 X 6 matrix with entries {1,..,36}.

Original entry on oeis.org

1859163031, 1859166733, 1859193211, 1859235497, 1859254067, 1859268659, 1859282869, 1859288597, 1859291519, 1859294309, 1859309245, 1859317037, 1859320819, 1859324083, 1859324501, 1859331797, 1859333683, 1859335879, 1859348273, 1859348639, 1859351059, 1859358869
Offset: 1

Views

Author

Hugo Pfoertner, Sep 07 2019

Keywords

Comments

There are 4521437 terms in the sequence.

Crossrefs

A088238 Numbers less than the maximum possible determinant A085000(5)=6839492 not occurring as determinant of a 5X5 matrix with elements 1..25.

Original entry on oeis.org

6773999, 6774223, 6774529, 6775471, 6775491, 6775877, 6776023, 6776291, 6776373, 6776557, 6776779, 6776803, 6777487, 6777655, 6777718, 6777731, 6778001, 6778103, 6778111, 6778781, 6778909, 6779065, 6779123, 6779261
Offset: 1

Views

Author

Hugo Pfoertner, Oct 03 2003

Keywords

Comments

The first term of this sequence is A088216(5).
The sequence contains exactly 38298 terms.

Crossrefs

Programs

  • Fortran
    c See link.

Extensions

Full sequence from Hugo Pfoertner, Aug 31 2014

A372708 a(n) is the smallest number k that is the concatenation of the elements of a 3 X 3 matrix whose determinant is n and whose elements are a permutation of the numbers 1 through 9; a(n) = -1 if no such number k exists.

Original entry on oeis.org

123456789, 123469857, 123467589, 123467895, 123458769, 123469578, 123589476, 123457689, 123748569, 123456798, 123469587, 123469875, 123458967, 123457986, 123469785, 123457698, 123548769, 123689574, 123546789, 123457896, 123569487, 123458697, 123547689, 123649758, 123567498
Offset: 0

Views

Author

Jean-Marc Rebert, May 11 2024

Keywords

Comments

The determinant of a 3 X 3 matrix whose elements are a permutation of the numbers 1..9 cannot exceed 412, so this sequence is finite.

Examples

			a(0) = 123456789 because it is the smallest number that can be formed by concatenating the elements of a 3 X 3 matrix whose determinant is 0 and whose elements are a permutation of the numbers 1..9. The matrix is [1 2 3] [4 5 6] [7 8 9].
		

Crossrefs

Programs

  • Mathematica
    a[n_] := a[n] = Module[{mat}, mat = Select[Partition[#, 3] & /@ Permutations[Range[1, 9]], Det[#] == n &]; If[Length[mat] > 0, First[Sort[ToExpression[StringJoin[Riffle[ToString /@ Flatten[#], ""]]] & /@ mat]], 0]];
    Monitor[(* Do not use Monitor[] if using Wolfram Cloud, otherwise memory issues may occur *)Table[a[n], {n, 0, 24}], {n, Table[a[m], {m, 0, n - 1}]}] (* Robert P. P. McKone, May 11 2024 *)
  • Python
    from sympy import Matrix
    from itertools import permutations
    adict = dict()
    for p in permutations(range(1, 10)):
        v = Matrix(3, 3, p).det()
        if v not in adict:
            adict[v] = int("".join(map(str, p)))
    afull = [adict[v] if v in adict else -1 for v in range(max(adict)+1)]
    print(afull) # Michael S. Branicky, May 11 2024
Showing 1-8 of 8 results.