A191966 Number of n X n symmetric (0,1) matrices that achieve the record mentioned in A191965.

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

Max Alekseyev, Table of n, a(n) for n = 1..37

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.

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

Corrected and extended to a(37) by Max Alekseyev, Mar 12 2023

Status

approved