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A333738
Number of non-isomorphic n X n nonnegative integer symmetric matrices with all row and column sums equal to n up to permutations of rows and columns.
1
1, 1, 2, 5, 33, 556, 31781, 5882230, 3589936407, 7347418294141, 51304793433150418, 1240428029662246026001, 105148289475978338858008298, 31582581551955332317665959184087
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OFFSET
0,3
LINKS
Table of n, a(n) for n=0..13.
EXAMPLE
The a(3) = 5 matrices are:
[0, 0, 3] [0, 1, 2] [0, 1, 2] [1, 0, 2] [1, 1, 1]
[0, 3, 0] [1, 1, 1] [1, 2, 0] [0, 3, 0] [1, 1, 1]
[3, 0, 0] [2, 1, 0] [2, 0, 1] [2, 0, 1] [1, 1, 1]
CROSSREFS
Main diagonal of
A333737
.
Sequence in context:
A366327
A197974
A208985
*
A114793
A254429
A298945
Adjacent sequences:
A333735
A333736
A333737
*
A333739
A333740
A333741
KEYWORD
nonn
,
more
AUTHOR
Andrew Howroyd
, Apr 08 2020
STATUS
approved
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Last modified August 4 08:16 EDT 2024. Contains 374905 sequences. (Running on oeis4.)