login
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, 29640619008000, 533531142144000, 101370917007360000, 101370917007360000, 425757851430912000, 3325168819675422720000
OFFSET
1,4
COMMENTS
Number of labeled squarefree graphs on n nodes with A006855(n) edges. - Max Alekseyev, Jan 29 2022
LINKS
PROG
(Sage) a191966 = lambda n: 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.
Sequence in context: A330367 A079322 A167304 * A333720 A135451 A175784
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
Corrected and extended to a(37) by Max Alekseyev, Mar 12 2023
STATUS
approved