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

Author

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

Keywords

• nonn

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

Crossrefs

Labeled version of A335820. Rightmost values in A352472.

Cf. A006786, A006855, A077269, A191965, A300756.

Programs

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

Extensions

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

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