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.

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A003433 Hadamard maximal determinant problem: largest determinant of (+1,-1)-matrix of order n.

Original entry on oeis.org

1, 2, 4, 16, 48, 160, 576, 4096, 14336, 73728, 327680, 2985984, 14929920, 77635584, 418037760, 4294967296, 21474836480, 146028888064, 894426939392, 10240000000000, 59392000000000, 409600000000000
Offset: 1

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Author

Keywords

Comments

I added the entry for n=22 since this has been proved optimal by Chasiotis et al (reference in A003432). [Richard P. Brent, Aug 17 2021]

References

  • Ed Hughes and Rob Pratt, New Features in SAS/OR 13.1, SAS Paper SAS256-2014.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • See A003432 for further references, links and formulas.

Crossrefs

A003432 is the main entry for this sequence.
Cf. A051753.
Cf. A188895 (number of distinct matrices having this maximal determinant).

Programs

Formula

a(n) = 2^(n-1)*A003432(n-1). E.g., a(6) = 32*A003432(5) = 32*5 = 160.
a(n) <= n^(n/2).

Extensions

a(19)-a(21) added by William P. Orrick, Dec 20 2011
a(22) added by Richard P. Brent, Aug 16 2021

A306838 Number of different values taken by the determinant of a real (-1,0,1) matrix of order n.

Original entry on oeis.org

1, 3, 5, 9, 25, 67, 233
Offset: 0

Views

Author

Steven E. Thornton, Mar 12 2019

Keywords

Comments

Every term in this sequence is odd, since 0 is a possible determinant, and if d is a possible determinant then so is -d.
a(n) >= 1 + 2^n, since every integer determinant between -2^(n-1) and 2^(n-1) is possible (see MathOverflow link).

Examples

			For n = 2, the possible determinants of a 2x2 matrix with entries from {-1,0,1} are -2, -1, 0, 1, and 2. Since there are 5 numbers in this list, a(2) = 5.
The possible nonnegative determinants for small values of n are as follows (all the negatives of these numbers are also possible determinants):
n = 1: 0, 1
n = 2: 0, 1, 2
n = 3: 0, 1, 2, 3, 4
n = 4: 0 through 10, 12, 16
n = 5: 0 through 28, 30, 32, 36, 40, 48
n = 6: 0 through 96, 98, 99, 100, 102, 104, 105, 106, 108, 110, 112, 114, 116, 120, 125, 128, 130, 132, 136, 144, 160
		

Crossrefs

Number of matrices having maximum determinant is in A051753.

Extensions

Edited and expanded by Nathaniel Johnston, Apr 19 2022
a(6) from Minfeng Wang, May 31 2024
Showing 1-2 of 2 results.