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 1-7 of 7 results.

A003432 Hadamard maximal determinant problem: largest determinant of a (real) {0,1}-matrix of order n.

Original entry on oeis.org

1, 1, 1, 2, 3, 5, 9, 32, 56, 144, 320, 1458, 3645, 9477, 25515, 131072, 327680, 1114112, 3411968, 19531250, 56640625, 195312500
Offset: 0

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Author

Keywords

Comments

The entries are restricted to 0 and 1; the determinant is computed in the field of real numbers.
Suppose M = (m(i,j)) is an n X n matrix of real numbers. Let
a(n) = max det M subject to m(i,j) = 0 or 1 [this sequence],
g(n) = max det M subject to m(i,j) = -1 or 1 [A003433],
h(n) = max det M subject to m(i,j) = -1, 0 or 1 [A003433],
F(n) = max det M subject to 0 <= m(i,j) <= 1 [this sequence],
G(n) = max det M subject to -1 <= m(i,j) <= 1 [A003433].
Then a(n) = F(n), g(n) = h(n) = G(n), g(n) = 2^(n-1)*a(n-1). Thus all five problems are equivalent.
Hadamard proved that a(n) <= 2^(-n)*(n+1)^((n+1)/2), with equality if and only if a Hadamard matrix of order n+1 exists. Equivalently, g(n) <= n^(n/2), with equality if and only if a Hadamard matrix of order n exists. It is believed that a Hadamard matrix of order n exists if and only if n = 1, 2 or a multiple of 4 (see A036297).
We have a(21) = 195312500?, a(22) = 662671875?, and a(36) = 1200757082375992968. Furthermore, starting with a(23), many constructions are known that attain the upper bounds of Hadamard, Barba, and Ehlich-Wojtas, and are therefore maximal. See the Orrick-Solomon web site for further information. [Edited by William P. Orrick, Dec 20 2011]
The entry a(21) = 195312500 is now known to be correct. [Edited by Richard P. Brent, Aug 17 2021]

Examples

			G.f. = 1 + x + x^2 + 2*x^3 + 3*x^4 + 5*x^5 + 9*x^6 + 32*x^7 + 56*x^8 + ...
One of 2 ways to get determinant 9 with a 6 X 6 matrix, found by Williamson:
  1 0 0 1 1 0
  0 0 1 1 1 1
  1 1 1 0 0 1
  0 1 0 1 0 1
  0 1 0 0 1 1
  0 1 1 1 1 0
		

References

  • J. Hadamard, Résolution d'une question relative aux déterminants, Bull. des Sciences Math. 2 (1893), 240-246.
  • F. J. MacWilliams and N. J. A. Sloane, The Theory of Error-Correcting Codes, Elsevier-North Holland, 1978, p. 54.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

A003433(n) = 2^(n-1)*a(n-1). Cf. A013588, A036297, A051752.

Extensions

a(18)-a(20) added by William P. Orrick, Dec 20 2011
a(21) added by Richard P. Brent, Aug 16 2021

A089472 Number of different values taken by the determinant of a real (0,1)-matrix of order n.

Original entry on oeis.org

1, 2, 3, 5, 7, 11, 19, 43, 91, 227, 587
Offset: 0

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Author

Hugo Pfoertner, Nov 04 2003

Keywords

Comments

Lower bounds: a(11) >= 1623, a(12) >= 4605, a(13) >= 14365, a(14) >= 44535, a(15) >= 145273, a(16) >= 476947

Examples

			a(7)=43 because a 7X7 (0,1)-matrix A_7 can produce the values abs(det(A_7))= {0,1,...,17,18,20,24,32}
		

Crossrefs

Cf. A003432 (largest determinant of (0, 1)-matrix), A013588 (smallest integer not representable as determinant of (0, 1)-matrix), A089478 (occurrence counts), A087983 (number of different values taken by permanent of (0, 1)-matrix).

Extensions

a(1)..a(4) from Wouter Meeussen.
a(7) verified by Gordon F. Royle.
Extended by William Orrick, Jan 12 2006. a(8) and a(9) computed by Miodrag Zivkovic. a(8) independently confirmed by Antonis Charalambides. a(10) computed by William Orrick.
Edited by Max Alekseyev, May 02 2011
a(0)=1 prepended by Alois P. Heinz, Mar 16 2019

A089477 Smallest positive integer not the permanent of a real {0,1}-matrix of order n.

Original entry on oeis.org

2, 3, 5, 13, 27, 119, 737, 5153
Offset: 1

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Author

Hugo Pfoertner, Nov 05 2003

Keywords

Comments

a(6) from Gordon F. Royle.

Examples

			a(2)=3 because {0,1,2} are expressible as permanents of (0, 1)-matrices.
		

Crossrefs

Cf. A089479 occurrence counts for permanents of (0, 1)-matrices, A087983 number of different values taken by permanent of (0, 1)-matrix, A013588 smallest number not expressible as determinant of (0, 1)-matrix.

Extensions

a(7) from Giovanni Resta, Mar 29 2006
a(8) from Minfeng Wang, Oct 04 2024

A108150 Number of different nonnegative values taken by the determinant of a real (0,1)-matrix of order n.

Original entry on oeis.org

1, 2, 2, 3, 4, 6, 10, 22, 46, 114, 294
Offset: 0

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Author

William P. Orrick, Jan 12 2006

Keywords

References

  • For references and links see A089472.

Crossrefs

A089472 is the main entry for this sequence. Cf. A003432, A013588, A051236.

Formula

a(1)=2, a(n) = (A089472(n) + 1) / 2 for n>1

Extensions

a(0)=1 prepended by Alois P. Heinz, Mar 17 2019

A373916 Numbers that are the determinant of real {0,1}-matrices of order 10, but not of symmetric such matrices.

Original entry on oeis.org

253, 268, 274, 294, 304
Offset: 1

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Author

Hugo Pfoertner, Jun 25 2024

Keywords

Comments

This property also applies to the corresponding negative values.

Crossrefs

A051236 Largest integer a(n) for which the integer interval [ 0,a(n) ] is a subset of the set of determinants of all n X n 0-1 matrices.

Original entry on oeis.org

1, 1, 2, 3, 5, 9, 18, 40, 102, 268
Offset: 1

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Author

Gerhard R. Paseman (paseman(AT)prado.com)

Keywords

Comments

A definition for a(n) is given in Craigen's paper. The table given there suggests a(9)=102. Term for term, this sequence is one less than the sequence A013588.

Examples

			There is a 7x7 0-1 matrix with determinant 20, but no 7x7 0-1 matrix with determinant 19.
		

References

  • R. Craigen, The Range of the Determinant Function on the Set of n X n (0,1)-Matrices, J. Combin. Math. Combin. Computing, 8 (1990) pp. 161-171.

Crossrefs

Cf. A013588.

Formula

a(n) = A013588(n) - 1

Extensions

Extended by William Orrick, Jan 12 2006

A215644 Full spectrum threshold for maximal determinant {+1, -1} matrices: largest order of submatrix for which the full spectrum of absolute determinant values occurs.

Original entry on oeis.org

1, 1, 2, 2, 3, 4, 6, 4, 6, 6, 7, 6, 7, 7, 7, 8, 8, 8, 9, 8, 10
Offset: 1

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Keywords

Comments

a(n) is the maximum of m(A) taken over all maximal determinant matrices A of order n, where m(A) is the maximum m such that the full spectrum of possible values (ignoring sign) occurs for the minors of order m of A.

Examples

			For n = 8 we have a(8) = 4 as a Hadamard matrix of order 8 has minors of order 4 with the full spectrum of values {0,8,16} (signs are ignored) but minors of order m > 4 do not have this property.
		

Crossrefs

Extensions

We calculated the first 21 terms of the sequence by an exhaustive computation of minors of known maximal determinant matrices as at August 2012.
Showing 1-7 of 7 results.