login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A333886 Number of non-isomorphic 4 X 4 nonnegative integer symmetric matrices with all row and column sums equal to n up to permutations of rows and columns. 2
1, 1, 5, 12, 33, 74, 163, 319, 596, 1044, 1754, 2820, 4394, 6629, 9756, 14018, 19743, 27286, 37111, 49707, 65699, 85756, 110691, 141382, 178882, 224309, 278990, 344342, 422000, 513718, 621506, 747493, 894105, 1063920, 1259823, 1484886, 1742533, 2036377, 2370431, 2748936, 3176544 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..40.

EXAMPLE

The a(2) = 5 matrices are:

  [0 0 0 2]  [0 0 0 2]  [0 0 1 1]  [0 0 1 1]  [0 0 1 1]

  [0 0 2 0]  [0 1 1 0]  [0 0 1 1]  [0 1 0 1]  [0 2 0 0]

  [0 2 0 0]  [0 1 1 0]  [1 1 0 0]  [1 0 1 0]  [1 0 0 1]

  [2 0 0 0]  [2 0 0 0]  [1 1 0 0]  [1 1 0 0]  [1 0 1 0]

.

The a(3) = 12 matrices are:

  [0 0 0 3] [0 0 1 2] [0 0 1 2] [0 0 1 2] [0 0 1 2] [0 1 1 1]

  [0 0 3 0] [0 0 2 1] [0 1 1 1] [0 1 2 0] [0 2 1 0] [1 0 1 1]

  [0 3 0 0] [1 2 0 0] [1 1 1 0] [1 2 0 0] [1 1 0 1] [1 1 0 1]

  [3 0 0 0] [2 1 0 0] [2 1 0 0] [2 0 0 1] [2 0 1 0] [1 1 1 0]

.

  [0 0 0 3] [0 0 1 2] [0 0 1 2] [0 0 1 2] [0 1 1 1] [1 0 1 1]

  [0 1 2 0] [0 2 1 0] [0 3 0 0] [0 3 0 0] [1 1 0 1] [0 3 0 0]

  [0 2 1 0] [1 1 1 0] [1 0 1 1] [1 0 2 0] [1 0 2 0] [1 0 1 1]

  [3 0 0 0] [2 0 0 1] [2 0 1 0] [2 0 0 1] [1 1 0 1] [1 0 1 1]

CROSSREFS

Row n=4 of A333737.

Sequence in context: A192303 A301785 A066280 * A192243 A292104 A136113

Adjacent sequences:  A333883 A333884 A333885 * A333887 A333888 A333889

KEYWORD

nonn

AUTHOR

Andrew Howroyd, Apr 08 2020

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 18 03:30 EDT 2022. Contains 353783 sequences. (Running on oeis4.)