

A191966


Number of n X n symmetric (0,1) matrices that achieve the record mentioned in A191965.


6



1, 1, 1, 12, 15, 900, 6615, 90720, 1995840, 1360800, 197920800, 359251200, 1297296000, 7264857600, 119870150400, 2615348736000, 2615348736000, 29640619008000, 533531142144000, 101370917007360000, 425757851430912000
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OFFSET

1,4


COMMENTS

Number of labeled squarefree graphs on n nodes with A006855(n) edges.  Max Alekseyev, Jan 29 2022


LINKS

Table of n, a(n) for n=1..21.


PROG

(Sage) def a191966(n): return sum( factorial(n) // g.automorphism_group(return_group=False, order=True) for g in graphs.nauty_geng(options=f'c f {n} {oeis(6855)(n)}:0') ) # Max Alekseyev, Jan 29 2022


CROSSREFS

Labeled version of A335820. Rightmost values in A352472.
Cf. A006786, A006855, A077269, A191965, A300756.
Sequence in context: A330367 A079322 A167304 * A333720 A135451 A175784
Adjacent sequences: A191963 A191964 A191965 * A191967 A191968 A191969


KEYWORD

nonn


AUTHOR

R. H. Hardin and N. J. A. Sloane, Jun 18 2011


EXTENSIONS

a(11)a(21) from Max Alekseyev, Jan 29 2022


STATUS

approved



